Digital Music — Editing

A Talk given at Callerlab 2008 and 2009

Moderator Kris Jensen and Panelist Clark Baker

This is the second of two sessions on this topic. This session is for those callers who have been using digital music for some time and wish to learn more about how to edit digital music. Attendees should have experience with using digital music and some understanding of the equipment used to play this music. The panel will expand on the equipment and processes which can be used to edit digital music. This session will provide more in-depth information designed for the more experienced digital music user.


Once music and speech have been captured digitally, there are many interesting ways they can be modified. Depending on the application, we may want to vary the tempo without changing the pitch, vary the pitch without changing the tempo, shorten the introduction, lengthen the piece by duplicating the body several times, remove certain sections, and perhaps merge several pieces together into a medley.

We assume that you are already familiar with the various methods of obtaining, digitizing, cleaning up, and playing music. This talk will cover the following topics:

We will be using the following tools. There are different versions of each available, some for free, some for a small amount of money, and some professional versions. The tools available for PCs differ in some cases from those available for the Mac.

Measuring Beats Per Minute

In square dancing we take one step for every beat of music. This beats per minute, abbreviated as BPM, is also referred to as tempo. Most of our traditional square dance music is recorded at 128 BPM which is slightly more than two steps per second. What if we want to change the tempo, perhaps slow it down slightly because our group moves a little slower?

When playing records, our square dance turntables allows us to vary the BPM by slowing the record down or speeding it up slightly. If a record is played at 45 revolutions per minute (RPM) has a tempo of 128 BPM, the same record played at 44 RPM will have 125.15 BPM. While this doesn't seem like much of a difference, dancers can and will notice this. Square dance tempo is an interesting and important subject by itself which we can't cover here.

Especially if we have obtained music from a non-square dance source, say from a pop music CD, we need to measure its BPM, and if necessary, adjust its BPM to our dance tempo. While you might expect there to be computer programs that automatically compute the BPM of a piece of music, I haven't found any that really work. Instead, the usual way is that you play the music and tap on a key, say the space bar, in time to the music and a simple program measures time and the number of taps and computes BPM. Our own Rich Reel provides a simple web application for free which accomplishes this task.

When I use this tool I am always amazed by how much the BPM varies as I am tapping. To get an accurate measurement, you should probably tap for 15 to 30 seconds or until the BPM number stops jumping around. If you are measuring pop music, be aware that the band can change tempo slightly as they play, often speeding up slightly. If it matters, you should measure the BPM at the beginning and end of the piece of music.

A really precise way of measuring BPM is to use a waveform editor, place a mark at the beginning of the piece on a beat, and place a mark a known number of beats later. For example, mark beat 1 of the opener in a singing call, and beat 129 which would be the start of the second figure. Using the waveform editor, select the region between the two markers and look at how many seconds long it is. We know it is 128 beats. We can now do the math with a calculator: beats / seconds * 60 seconds/minute = BPM. This assumes the tempo didn't change over this time interval.

Changing BPM

There are two reasons we may want to change the tempo of our music. As callers we are used to having a variable speed turntable and adjusting each record for the particular group we are calling to. Certain records we know are recorded slightly fast and we need to slow them down a bit. Certain groups or areas of the country dance a few BPM slower than usual and some teen groups like things a bit faster. The second reason is that we trying to use alternative music for patter calling and it isn't close enough to our usual dance tempo.

Those of us who play digital music with a player that allows real-time tempo changing can ignore reason #1. For now, let's assume that we are changing tempo due to reason #2.

When we use the variable speed control on a turntable, CD player, or mini-disk player to adjust the tempo, the pitch also changes. Except for people with perfect pitch, and as long as the change is minor (say up or down no more than 4 BPM), this pitch change can be acceptable. However, digital editing does tempo changing one better. Certain digital editing programs allow us to change BPM or pitch independently of each other. We will focus on changing BPM with keeping the pitch the same.

Without describing the exact commands for a specific tool, you will read the music into the program, set a tempo control slower or faster (often measured as a percentage), listen and make sure you like the result, and save the result out under a new name.

Assume we measured our source music at 116 BPM and we want it at 128 BPM. We would calculate 128 / 116 * 100 = 110% and set the tempo slider at 110%. Then we would listen to the result and, if it sounds good, tap out the new BPM to make sure we hit our target. If all is well, we would save the result.

Changing tempo without changing pitch can have some trouble areas, especially when the changes are great. Always be on the alert for each of these:

Audio artifacts: Depending on the music, the program, and the amount of change requested, the resulting music can contain certain sounds that were not present in the original music, and are annoying to all listeners. Sometimes these can only be heard when listened to with your real output system and speakers at dance levels. For this reason, listening to the results of your edits and transformations should be done with a good sound system, not just laptop computer speakers. If you do get artifacts, you can try different settings in the program, or even a different program. Loss of energy: Sometimes when you slow a piece of music down, it loses energy. While the original piece makes you want to stand up and dance, the slowed down version sound draggy and, while it may be 128 BPM, it doesn't make you want to dance. Not the original: People who are really familiar with a given piece of music will notice if you speed it up or slow it down too much. While this may not bother most people, it may really bother a few.

Marking musical phrases

I like to go through a piece of music and drop a marker at the beginning of every 16 beat phrase. In Sound Studio one can type Command-M while the music is playing to drop a marker. Its position will only be as accurate as your typing, but as long as it is near beat 1, you can adjust it later.

You will learn a lot about your music if you try to characterize each of these 16 beat phrases. For example, in contra dance music, most tunes are composed of 4 16-beat parts: A1, A2, B1, and B2. A2 could be a repeat of A1 or it could be slightly different. The B's sound different than the A's. With traditional MWSD patter music, you may find it changes every 32 beats, perhaps by featuring a specific instrument, modifying how the underlying percussion is accomplished, or playing with the melody.

Most music has an introduction and an ending. Sometimes these need to be edited for our purposes. For example, the introduction could be too long and needs to be shortened. Occasionally the music can contain sections that won't dance well. For example, the underlying beat could be subdued or lost altogether. These will need to be edited out. As the music transitions from one part of the song to another, there may be a musical bridge. There would be an extra 4 to 8 beats of music that accomplish this transition. As a caller we need to know how to work with this transition, or we can remove it.

In order to accomplish any of the above, you need to mark your music, characterize the pieces, and decide what edits you want to perform. Remember, we can't create any new music or notes. We can only use what was in the original music. However, we still have a lot of flexibility.

Cutting and pasting

You can only have seamless edits if your markers are placed precisely. The easiest edits are on the beat. We want to make sure the marker is placed just to the left of the beat. In each piece of music, the beat looks different. You want to place the markers in the same relative position to the beat. If "1" is the most zoomed in (where each pixel on the screen corresponds to one audio sample value), I usually work at "32" or "64" when positioning a marker around a beat. Note that one beat is around 24,000 samples!

Editing is done around two markers. Either we are going to delete the audio between markers, or we are going to save it and duplicate it. Before doing either operation, we want to make sure we have an exact piece of music (in terms of beats) between the markers. First zoom in on each marker and adjust it so that it is as precise as you can make it. Next zoom out so that both markers are on the screen. Select the region between the markers, set the playback option to "loop", and start playing from about 8 beats before the right marker. Listen carefully as it jumps from the right marker back to the left marker. If you did your job right, the jump should be seamless with respect to the beat of the music. If not, you must adjust the markers and figure out what you did wrong.

Just because your edits are on the beat, doesn't mean that they will work. Perhaps there are some vocals and your edit will sound bad. Perhaps the instruments that are playing change suddenly and the edit sounds bad. In addition to listening a few beats before and after the edit, you need to step back and listen to your final edited piece from start to finish. This is done by doing the best you can while editing, saving the entire piece and listening to it a few days later, say while driving in the car. This fresh listen will let you know if you have made any jarring edits.

Sometimes placing markers on beat boundaries is not going to work, even when you can do an accurate placement. If the sound has vocals, and if the vocals start before the beat, then performing edits on the beat will make the vocals sound funny. In this case, I have backed off the beat by a known amount for each marker and done the edit there.

In special cases, I have edited beat by beat and, for example, stretched an 8 beat bridge into a 16 beat phrase. This is rare. Most edits are at the phrase level (16 beats).

If you wanted to lengthen patter music, you could place a marker on beat 1 after the intro and another marker at beat 1 of the ending, and copy the entire body 3 times. This would turn a 3 1/2 minute patter into 12 1/2 minutes.

Remember to pay attention to the beginning and ending of the music you edit. Contra dance music usually starts with 4 potatoes or notes that set the tempo. MWSD patter records often have 16 beats of opener. Endings can be abrupt or fade out. If your music doesn't have a good ending, it is easy to edit in a short or long fade.


Equalization is the process of increasing or decreasing the level of certain frequencies or tones compared to other frequencies. For example, if your source music sounds to bassy, you may want to decrease the bass. Your Hilton has a knob labeled "Bass" which can do this adjustment. You probably already play some music for which you know that you have to adjust the Bass and Treble knobs a certain way. If you want, you can digitally modify your music once and for all with these types of adjustments.

Instead of just turning a Bass knob and a Treble knob, Sound Studio offers a 3-Band Equalizer, a 10-Band Equalizer, and a Graphic Equalizer. The "bands" refer to the number of knobs or sliders. The 3 bands are Low, Mid, and High which adjust low notes and sounds, mid-range sounds (like speech), and high notes. The 10 bands give you finer control. Normally adjacent sliders are set somewhat close to each other so the 10 form a smooth curve, perhaps decreasing the low notes, boosting the midrange, and slightly decreasing the high notes. The Graphic Equalizer lets you specify such a curve with as much detail as you want.

Some programs allow you to play the music, move the sliders, and hear the results in real-time. With others you need to make a change, listen, and possibly "undo".

Creating Medleys

If you want to join two or more separate pieces of music to create a mix or medley and still keep it danceable, you need to pay attention to several areas. For this discussion, assume we have two pieces of music, the one that comes first and will be on the left side of our waveform window and the one that comes second and will be on the right side.

The two pieces of music must share something in common. Their underlying rhythm and way their beats are produced should be the same.

You must make sure the music that will be danced second has a BPM that is the same as or slightly greater (say 1 BPM more) than the music that will be danced first. If not, it can feel like dancing into molasses when dancers encounter the transition.

You need to find a transition point in each piece of music. Instrumental works better than vocal. Often having the left music loop back towards its beginning structure and then transition to the right music can work. DJ's often use a cross fade to transition from one piece of music to another. I have rarely been able to use this effectively with dance music. Expect to spend a lot of time editing a good transition.

After they are merged, check the volume levels and adjust so that they match. Also check to see if any equalization is necessary.


With the right programs, audio editing isn't that difficult. You get instant results and can hear what you have done. You can spend a lot of time at it, but the results can be worth it. Learn how the different commands work as you need them, and find someone more knowledgeable than you for questions and general concepts.

Revised: $Date: 2009/04/03 06:22:46 $