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The objective of this unit is to provide you with a few more concepts that will help you create a strong sounding mix, particularly through the use of Reverb and additional compression techniques.  As you progress through the material, consider taking notes, test out the techniques, and report your discoveries.  For every concept, I have provided you with resources to assist you.  Please go deeper and research any concepts that may be a challenge or of interest to you.  To receive credit for this work,  you will need to provide evidence that you understand the material, and can ultimately use it.  Be sure to find your instructor to review your work at the end of the unit. 

Skills and Understandings 1: 

Reverb as a tool to emulate acoustical environments to create the sense of space.


Reverb adds reverberation (rapid, modified repetitions blended with the original sound that gives an impression of ambiance).   

Applying a small amount of stereo reverb to an untreated mono signal duplicated into a two-channel stereo track will usually make it sound more natural.


I understand the basic concept of Reverb and how this tool came to be.


I can locate the primary functions of a reverb plugin to manipulate the settings required for the type of track that I am modifying

Key Reverb Parameters

The important reverb parameters generally placed under user control are early reflection pattern, pre-delay me, overall decay me and high-frequency damping.


Pre-delay refers to the time between when the original sound starts and when you hear the first of the reverbs ‘early reflections’. The greater the pre-delay me, the larger the perceived room size: imagine how in a large space such as a hall or a cathedral it will take longer for the sound to reflect back as it has more distance to travel.  Increase the pre-delay me to put a bit of separation between the original sound and the reverb – this way you get the spacial benefits of reverb without it cluttering or masking the mix (particularly useful for vocals and lead lines).



Early reflections are the first distinct echoes heard at the onset of the reverb.  No early reflections are heard until the sound has reached the nearest wall or obstacle and reflected back to the listener. This initial delay between the direct sound and the first reflected sound provides what is perhaps the strongest clue as to the room size: if the reflection returns as a distinct echo, it suggests that the reflective surface is both solid and flat. A more diffuse echo (one with less pronounced individual reflections) suggests irregular surfaces. The greater the spacing of the early reflections, the larger the ‘space’ sounds.


Reverb time or decay time refers to the time it takes for the reverb tail to dissipate into silence. It’s not actually very easy to say when a reverberant signal finally disappears, so there’s a standard measurement of reverb decay known as RT60: this sounds like a component of some complex equation, but it simply means the time taken to the level of the reverb to decay by 60dB. Simple!
Long decay times work well on sustained sounds but. When you first start playing with reverb it seems obvious that a long overall reverb decay me is the best way to create the impression of a large environment – but this is also the quickest way of filling up all the gaps in your track and creating a big mush. In fact, as already mentioned above, as much depends here on the early reflections to tell us how big a space seems to be. For example, a small led bathroom will be very reflective and so may have almost as long a decay me as a large hall – but the nature of the early reflections and the brightness of the following reverb tail are what give us the clues as to the room’s actual size. Speaking of brightness...

Key Reverb Controls


Wet - this is the amount of the reverb effect being applied to a sound

Dry - this is the initial sound before it is effected by a reverb plugin

Mix or Wet/Dry controls are simply where you choose the proportions of the original sound and the reverbed sound. If you have your reverb plugin set up as a send effect, the Mix knob should be set to 100% / Wet, as you’ll be controlling the proportions based on how much "level" you send from each individual track.


Room size - The room size should be adjusted according to the decay time. Small room size with shorter decay, large room with a longer decay. 


Pre-delay - This controls the time of the delay in the reverb and should be adjusted according to the room size. Less pre-delay for smaller rooms, more for larger rooms.



Low cut - Takes the base out before the reverb is added.

Low-frequency damping o en appears next to the high-frequency damping control. This can be very useful for shelving o some muddying lows and mids and help you shape the reverb to fit the part and the track overall.



High cut - Takes the treble out before the reverb is added.  

High-frequency damping allows the high frequency decay me of the reverb tail to be made shorter than the overall decay me. This emulates the way the surfaces and materials in real rooms absorb certain frequencies. Adjust this parameter for more or less realism, and also to color the reverb as ‘bright’ or ‘dark’ to fit it into the mix (more on this shortly). It is basically a high-shelf EQ built in the reverb, but you could certainly use a separate EQ plugin for this after the reverb for greater control if needed.


Diffusion - Makes echo sound close so that it sounds like white noise. distorting the echo.

Decay - Controls the decay time of reverb.

Reverb Preset Types



The hall reverb is one of the most commonly used types of reverb. As the name suggests they are designed to emulate the reverberation effect of large halls, or other large spaces such as theaters or even churches. Real life reverberation in a concert hall is characterized by a long reverberation, and hall reverb setting that emulates that environment will do the same.


Since these types of reverbs are great for modeling large natural physical spaces, it’s no wonder that they are a common go-to reverb. However, it’s important not to get carried away when using them. If you apply too much of a hall reverb in a mix the long reverberations can make your mix sound too distant or drowned out, or just plain muddy.


Hall reverbs are rich, warm and big. They are generally a good choice for adding some three-dimensional ambiance to your mix.  Because they are big, they are often used to fill out the back end of your mix  – adding some depth without overpowering the front of your mix.




A room reverb is similar to hall reverb, normally designed to emulate the reverberation of something being recorded in a room. Because they are emulating smaller spaces than halls, this results in the reverberations being much faster with faster decays. (Think of clapping your hands in a small room versus a church and how that would sound). For this reason, things like drums and guitars are good candidates for room reverbs.


Room reverb is a great choice to add some realism to instruments that are recorded by a microphone in very close proximity to the instrument and are also very good for adding some character to an instrument that is recorded directly into our sound card or DAW. A decent room reverb will give the listener a sense that the instrument is being played in a real room.


A common parameter in reverb units that you shouldn’t overlook is is Pre-delay Time. Good use of this will allow you to add sufficient room reverb to your instruments but still keep them sounding “present” in the mix. Pre-delay allows you to specify the amount of time between the start of the direct sound and the start of the first sonic reflection. By increasing the Pre-Delay, you can create a small gap between the initial onset of your sound and the beginning of the reverberations – what you are looking for is a nice blend between the two that makes your instrument sound “close” but also gives the listener a sense of the “room” it’s in.



Plate reverbs emulate very early methods of generating a reverb.


Plates have a similar sound to hall reverbs that is usually denser and flatter and more two-dimensional sounding. They are clean and bright sounding and are great at adding some overall length and size to a sound without it making it sound distant or small.  As a result, they often sound amazing on vocals or snare drums – and because they are different to hall reverbs and don’t add the same feel of distance or depth they can often blend better with the original sound.

As a result of their unique characteristics, plate reverbs are making a bit of a come-back now that more accurate digital emulations are now available to the “in the box” producer.



Spring reverbs simulate a method of generating reverb that is commonly built into guitar amplifiers, by injecting sound into metal springs and letting them reverberate. Spring reverbs tend to sound bouncy and lo-fi. They can also be “ringy” and feedback into themselves.


Spring reverbs are typically used on individual instruments rather than full mixes. Used on guitars, they can add a twangy bounce and liveliness. For instruments such as electric pianos and organs, spring reverbs can add a vintage depth and dimension to the sound. They’re usually not used with drums or vocals because the sound is not as smooth as other reverbs. On the other hand, you might want to try it out for a strange or psychedelic effect!

Too much spring reverb in a mix will make it sound lo-fi or distant… but that might be exactly what you’re looking for!


Reverb Types


I can apply the fundamentals of reverb control to a variety of types of reverb units.

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Algorithmic, Convolution, & Modeling Reverbs

There are different types of reverb units and plugins to choose from because of the different approaches that have been created to artificially simulate natural reverb. Before electronic units and computer plugins, electro-mechanical spring and plate reverb and echo chambers were the only ways to introduce reverb to recordings. Fortunately, things have moved on considerably since then, but these older mechanical reverbs had a charm and sound of their own that is still sought after n the digital domain. This is where emulations and vintage modeling plugins become used.


Algorithmic reverbs use calculations based on hypothetical rooms and other spaces to generate their reverb sounds. Generally, this gives a sharper, more artificial sound, typified by most hardware digital reverbs of the last 30 years. This is not necessarily a bad thing though – musically we’re not always after the most ‘natural’ sound, but the one that has the right ‘character’ for the track. In fact, algorithmic reverb can be easier to place in a mix because it isn’t as realistic as convolution reverb! Algorithmic reverbs also tend to be the lightest on the computer’s CPU, a significant consideration when you’re using several instances in a busy mix.


Convolution reverbs use pre-recorded samples of real rooms and spaces to build Impulse Response (IR) files of those spaces. The impulse response is then ‘convolved’ with the incoming audio signal you want to process, hence the name.
Convolution reverbs then, are generally far better at simulating real spaces than algorithmic reverbs – the only major downside is that they also require significantly more CPU processing power.


Generally, then you’ll want to use convolution reverb where a lifelike quality is important – for example, you can simulate the effect of a set of ambient room mics (more on how to this on the following pages). Convolution reverb can take a bit more work to sit in the mix than a good algorithmic reverb – it can easily be a bit heavy in the low mids and lack high-end sparkle, as this is how real reverb tends to sound.


Modeling reverbs are designed to replicate the characteristics of particular vintage hardware reverb units, such as the Universal Audio EMT 140 modeled on a real mechanical EMT plate reverb, or the spring reverb emulations found in many guitar amp plugins. These reverbs can provide a fantastic contrast to the relatively soulless digital perfection of algorithmic or convolution reverbs, bringing additional character and nice tonal shaping to whatever you run through them





A Look at Convolution vs. Algorithmic Reverb
3 Dimensional Reverb Use

Apply reverb to your mix project and/or recording project in a manner that best represents what you have learned in this section. Listen carefully to make sure that you do not mask other parts.   Additional information is presented below for you to expand your knowledge of reverb. 


Remember to provide evidence of your learning

to pass this proficiency level. 


I can apply appropriate Reverb or Delay to my projects to create space or a unique audio effect. 

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This video is very interesting

If you can use Reverb or Delay as a tool to emulate acoustical environments to create the sense of space, then you have met this proficiency.

When to Use Delay Instead of Reverb to Create Room in a Mix


Why Do You Need Space in the First Place?

Whether you’re using reverb or delay, the goal is to provide more space in your mixes. Both tools are designed to recreate the effect of sound waves traveling through the natural space of a room, providing a more natural sound to your recordings.

But the use of reverbs and delay also color the entire sound of your mix, providing ambiance to a track that can build the underlying emotional feel of the song. While reverb tends to be the go-to tool for many engineers, here are a few times you may want to try delay instead.


To Avoid a Washed Out Mix

Using too much reverb on your tracks can quickly result in a “washed out” sound. While this occasionally can be what an engineer is going for, you typically want to use reverb and delay to make a more natural sound, not a muddy mix. Delay can be a great way to avoid a cluttered mix because it can keep the instruments up front while adding some ambiance. The tip of using a slap-back delay below is a good example of how to do this.


On a Fast Vocal

Applying some reverb to a vocal is a great way to help it “sit” correctly in your mix, but occasionally this can do more harm than good. For example, on faster vocals, the reverb often gets lost in the mix, until you turn it up so much that it no longer gives you the sound you want.

When this happens, a great solution is to add a delay. This way you don’t make the delay as prominent, but it still serves its purpose in the mix. A slap-back delay – featuring a single delay sound – can be a great way to do this without muddying up your vocal.


For a Big Guitar Sound

If you’re a fan of The Edge and his guitar sounds for U2, you’ve probably already considered putting a delay on your guitar. Similar to vocals, too much reverb can make a guitar sound too distant and lack the impact it needs to have. A delay, however, can amplify that impact while still making the track seem much bigger and roomier than the dry track.


Use Delay and Reverb

While delay and reverb tend to be an either/or proposition, you can occasionally use both to great effect for certain tracks. For example, after finding a great delay, tack on a small room reverb. This can come in handy if the delay is coming through a bit too sharp in your mix. Beware, however, that adding too much reverb can quickly take your track from a place where it sits nicely in the mix to a washed out mess.

Skills and Understandings 2

The Final Mix and Mastering Process



Option 1: Test your mix in mono! Use the MONO button on the output channel to sum the channels together into one (MONO) channel. This will put all sounds into the center.

• Listen for Comb filtering or phase cancellation

• Listen for any sounds that may have disappeared 


Option 2: Level all your tracks to unity gain (O dB) and then pan each track to the left, then right. Listen to see if each sound sweeps audibly from the left, through the center, and off to the right. If you can hear the sound of the track crossing across the audio spectrum without timbre compromise, then the track is probably fine and needs no adjustment.


Option 3: Use your ears and knowledge of instrument and vocal timbres to locate trouble spots


Compare your mix to an original. 

Please note that you have not really "Mastered" the track.  That is a completely different process that happens after the mix is completed. Mixing and Mastering are different stages of the process.  We will look at mastering next...  


Check for Masking

Sometimes mixing is a matter of hearing your music in a few different ways, to bring out any changes that need to be made. One of the simpler tricks to do this is to listen to your mix in mono toward the end of the mixing process.

Most DAWs or mixing boards have a button to test your mix out in mono. It’s there for a reason!


Here’s why:

Mono Can Reveal Comb Filtering

When two tracks are in the same frequency range and out of phase with each other, it can cause a kind of audio signal interference called comb filtering.  Comb filtering is a thin and weak sound in your mix.

Sometimes when you’re mixing in stereo it can be harder to catch any comb filtering taking place in your tracks. By removing the added dimension of stereo, it helps to really identify any occurrences of interference.

Mono Can Reveal What’s Still Needed

The added dimension of stereo can add a lot to a mix. But sometimes it can also serve as a crutch that hides what’s missing from the mix. By dropping the stereo field and checking your mix in mono, you can get a clearer picture of how your tracks are interacting with each other and what still may be needed to “glue” everything together.

Mono Can Failproof Your Mix

It’s a lot easier to get a great sound when you’re sitting in a treated room with two high-quality monitors spaced evenly. The problem is that listeners won’t be hearing your music in that setting over 90% of the time.

Think of mono as your worst-case scenario. If you can get your mix to sound balanced in mono, then adding stereo will only make it sound better. But even in those instances where listeners are in less than ideal listening settings, you can know that they’re still getting a good experience of your mix.

Mixing in mono is one of the easier ways to check that your mix is in good shape. Some producers even recommend only mixing in mono at first before going to add stereo. Some live venues have their PAs set up for only mono.

The key to having a great mix and master is versatility. It has sound great on as many systems as possible. Using mono mixing to get a better picture of the balance of your tracks is one of the best ways to ensure that your music is truly versatile.


I can test my mix for masking issues


I can prepare my mix for final mastering


Most engineers sned their final mix to a mastering engineer.  An experienced, talented mastering engineer can work a lot of magic, but he can’t fix a really crappy mix, so here are some points to think about:


* Make sure everything is in tune! If a guitar is out of tune or the vocalist hit a few off notes, you will still hear them after mastering, and if you are like me, they will make you cringe every time you hear the song for the next 20 years. Some people use flex pitch or Celemony Melodyne single-track plugin. It works wonders if you have to correct the odd vocal or lead guitar note in an otherwise great take. It can also fix a rhythm guitar that is slightly out of tune. I have also used it when I had different takes of the same song on different media and wanted to combine them even though they were slightly out of tune with each other and at different tempos. It was a painstaking, section by section and bar by bar process, but I used Melodyne to fix the tuning and Logic Pro’s “Time Stretch Region to Locators” function to sync the tempos.


* Be tasteful, even conservative with effects, use them wisely. And while having a good reverb sound is important, it doesn’t mean using so much that everything sounds like mush. A little chorus on the electric piano or rhythm guitar, maybe some stereo delay on the vocals, are all good. But just remember that whatever effects you use now, you are stuck with them, the mastering engineer can’t undo them later.


* If you want to warm your mix up a little, especially when everything was recorded digitally, there are a lot of different tube and analog emulation plugins; some people use Airwindows BussColors, PSPaudioware Vintage Warmer II and Waves Kramer MPX, but be careful as some of these do add compression and change the dynamics of the mix. You can always ask the mastering engineer to do this for you. Some will even run the final mix through an old 1/2 track tape mastering deck to give it that tape sound.


* Careful use of EQ and panning will open up your mix. For most styles of music, you should be able to hear every instrument clearly. Everything should have its own place in the mix, you don’t want a lot of things competing for the same frequency range, that is what makes mixes sound muddy especially in the mid-range. Leave holes, let your music breathe.


* Do not use a lot of compression and definitely don’t use a limiter on the master buss! That is the mastering engineer’s job. If you squash the poop out of your mix, he can’t magically put the dynamics back later. It is his job to give your music it’s final loudness and presence. He needs some headroom to work with. Go to the loudest part of your song, usually that big chorus near the end, and make sure your mix peaks at -3 or -4 Db or less. It is also the mastering engineer’s job to do the final EQ’ing, balance the mix sonically, and fix any phasing or problems with the stereo imaging. Don’t use harmonic distortion, stereo spreaders or any kind of loudness maximizers (just another type of limiter) on the master buss either, again these are the tools of the mastering engineer; let him do his job!


* When you bounce your final mix, use the bit rate and sample rate you recorded it at.  If your project was recorded at 24 bit, 48 kHz, your final mix should be at the same bit and sample rate. The mastering engineer will deliver it back to you in a 16 bit, 44.1 kHz stereo wave file format (and also at higher rates if you specifically ask for them). Your mix should be a stereo interleaved wave file. Do not use any dithering. Make sure normalize and any other options like, “Include Audio Trail” are turned off.


* Sleep on it! A day or two after the mixing session, when you’ve gotten some sleep and your ears are fresh, double check your final mix on as many different systems and speakers as possible: your studio monitors, headphones, home stereo, your iPod and car stereo. You might have to turn it up a bit as remember, it peaks down at minus 3 or 4 DB, but it should sound good on everything you play it on and be fairly consistent. Listen to it at very low volume and make sure nothing is jumping out at you or too low in the mix. I have a 30 year old pair of Auratone near-field monitors that I use for just this purpose. Play it for other people whose musical opinions you trust.


* Send your mix to the mastering engineer via a large-file-send program like YouSendIt or via FTP depending on his preferred method of delivery. Include any notes you might have about your song and what you are looking for. It doesn’t hurt to reference some bands and songs that sound similar to yours or that you would like your song to emulate sonically, e.g. I want the lead vocal to cut like, “Cold as Ice,” by Foreigner or I want the guitar solo to sound like Pink Floyd’s, “Comfortably Numb.” This really helps the mastering engineer know what you are looking for. But be realistic.  






So, now, what is the difference between a compressor and a limiter?  We now know that a compressor controls the dynamics of a source.   A limiter does the same but in a more extreme manner by not allowing any signal past the threshold. This is why you will often hear the term “brick wall limiting”. It acts like a brick wall in that it lets absolutely nothing pass.


Since limiters do not have an attack control, the instant the signal crosses the threshold the limiter immediately prevents any additional level increase. Just like a compressor, many limiters will have a release control to set the time it takes after the signal goes below the threshold for the limiter to completely stop attenuating.


You will find limiters in use in mastering, broadcast, live sound and other situations where level control is required to prevent clipping, hefty fines, or blown loudspeakers.


DOES YOUR MIX STILL NEED WORK?  Here are some advanced techniques you can try




Let’s start with parallel compression.  Parallel compression is the process of duplicating a track, compressing one of them, then playing it back at the same time as the uncompressed track. But what is the value of parallel compression? One common reason is to increase the perceived volume of a track without compromising the dynamics with a limiter. Even though you can accomplish this in part by just using a compressor on the individual track, sometimes you can’t get it quite loud and punchy enough without distortion and unwanted side effects.  Parallel compression gives us the best of both worlds: the clean, transparent sound of the original track plus the richness and presence of the compressed track.


  1. Highlight all of your drum tracks      (I put all of mine in a track stack first - folder stack)

  2. Go to the mixer window - press x to open it.

  3. All the drum tracks should be highlighted.

  4. Add a send to BUS 10 on one of them ... this will add a bus to all highlighted tracks

  5. Change the Aux track to a Stereo track by 

  6. Turn up the send knob on one track to turn them all up.

  7. Bypass any compression you did previously on the drum tracks. ( Turn off compression)

  8. Add a compressor to the new Aux track which is probably called Aux 1.

  9. Change the send on one track to Prefader... should change them all.

  10. You now have dry tracks going out and an Aux track that has a compressor on it.  You can compress the entire kit at once while maintaining the original dry signal.

  11. Play around with the balance between the compressed and uncompressed tracks to find what you like.  If you have a track stack, you can lower the entire kit's dry signal at once to hear only the compressed Aux track.  




Now let’s take a look at multi-band compression. The term “multi-band” refers to the fact that multiple bands of frequencies can be compressed independently of each other. You compress the low, mid, and high frequencies all with different parameters or leave some alone while focusing on those that need attention.

Most multi-band compressors will have 4 or 5 bands. Each band will have completely independent controls, meaning that you can have a different ratio or attack speed for your mid and low frequencies, and so on.










The Process Of Mastering Audio


The Process of mastering audio involves a series of steps that have not changed very much over the decades. What has changed is the tools used, the medium worked with and the end product that is released to the public. While the mediums have evolved and the number of ways we can master audio has increased, the basic steps remain. Let's review those step one by one and show how they have developed over the years.




  1. Prepare The Master Mixes  -Computer based mixes must be examined for sample rate, bit depth, and file format to determine if the best quality format has been presented.

  2. Transfer - The transfer process, for mastering audio, has been greatly simplified over recent years as a majority of final mixes are presented as digital audio files on a hard drive.

  3. Set The Song Order - if you have multiple songs

  4. Edit -Once the masters are transferred, the files will need to be edited so that the start and end of each song are clean. There is usually a short breath of space left in at the beginning of a song, with a fade-in, to smooth the transition from silence. End edits involve getting rid of extra noises and chasing the ending with a fade-out to conclude the song naturally.

  5. Set The Space Between Songs

  6. Processing -Mastering audio can also involve a bit of processing when called for. The motto of the mastering engineer when processing is always the same, do no harm. Processing generally comes in only 2 forms even though those 2 forms can serve a large variety of purposes. The 2 forms of processing are compressors and equalizers.  Compressors serve an enormous number of purposes when mastering audio. A compressor, when used lightly, can add overall level and power to a mix. In the form of a peak limiter can be used to control peak levels that allow the overall gain of the song to be increased. In the form of a multi-band compressor, it can be used to strengthen a frequency area that is deficient in the mix.   Equalizers also serve many purposes in mastering audio. An EQ can be used to subtly shape a frequency area of a mix to add clarity and depth. It can also be used to filter out low frequencies that keep a mix sounding muddy or lacking in punch. A notch filter may be employed to remove a troublesome frequency in a mix.

  7. Levels PQ and ID Coding:  Make sure that the overall levels from song to song are even. This is not as easy as it may seem on the surface. The frequency content, density of frequencies and amount of compression can lead to uneven balances that require a good ear to get right. Additionally, a fade in or fade out on one song can skew the perceived level of the next. The difference between perceived level and actual level can easily lead to bad decisions if only looking at the meters for reference.    The PQ coding and ID tagging process allow CD Text, ISRC codes, UPC/EAN and Copy Protection data to be entered into the instructional data of a CD or downloadable file. ID tagging allows downloaded digital audio files to be identified in terms of song name, artist, songwriter, date recorded, musical style, etc… The tagging can also allow for ISRC and UPC/EAN coding so that sales and radio play can be tracked by the owner of the recordings.

  8. Dithering -A great way to preserve the quality of higher resolution masters is to apply a process called dithering. Dithering is a process that involves adding low-level random noise to the audio when lowering the bit depth from 24 bit to 16 bit as required for CD mastering. The added randomness helps preserve the sense of depth in a mix that is normally found with higher bit depth masters. It is always the very last step of the mastering audio process before printing the final production master.

  9. Create The Final Production Master -The final stage of the mastering audio process is to burn the final production master. The final product of the mastering session can be a burned PMCD or a DDP file. PMCD stands for Pre-Mastered CD which is formatted specifically for the manufacturing plant and used to create what is called a glass master. A high-quality disc burner, and CD media is an absolute necessity to keep the error count low.






Mastering Process

Mastering Audio Projects
Mastering your own tracks


I can do basic mastering on my projects

Time to wrap it up.  Once you believe you have mixed and mastered your project.  Post it online.  Be sure to provide evidence that you understand the mixing and mastering process. 

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