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Making Perfect Loops with the Digitech JamMan
and Sony Sound Forge Studio

By Norm Bowler, March 2008

Introduction

The Digitech JamMan is a digital looping pedal. Starting with either nothing or a preloaded loop, you can play pre-recorded phrases over and over, add new parts in a sound-on-sound process, and play live over the result. With a little planning and practice, one person can sound like a whole band. It's great fun, musically impressive, and it allows you to share your creative process with your audience: they get to see and hear the song being built instead of just hearing the finished product.

The hardest thing about looping is getting the loop point exactly right -- starting and ending the loop precisely on the downbeat. Manufacturers of looping tools know this, and add click tracks and even-measure boundary points. But in order to use them, you need to play your first track to the click, then either leave the click in or reach down to turn it off at the floor pedal. It can get cumbersome.

I prefer an easier way -- since a full band sound will include some sort of percussion, I plan my drum loops in advance, pre-record them, and load them to the JamMan via its USB interface from my computer. This has numerous advantages -- the loop points are perfect, and I can start my song with one track already laid down, meaning the audience doesn't have to watch me lay in 8 or 16 measures of drum machine before I can do anything else.

In this article, I will explain all the tricks to making perfect JamMan loops of drums, full band arrangements, or anything in between. What you learn from reading this will help you take your looping performances to the next level of professionalism.

Tools You will Need

  • Digitech JamMan Looper
  • USB cable to connect the JamMan to your computer
  • Digital audio editing software

I use Sony Sound Forge Audio Studio version 9. I'm sure other programs will work, but I recommend SFS9 very highly, and you'll see how well it works for our purposes as we proceed. All the examples and instructions will be based on Sound Forge Studio. You can buy SFS9 at Amazon.com.

This is a Windows program -- sorry, Mac folks, I'm not familiar with a Mac alternative. Also please note that SFS9 does not do multi-track recording. It's a professional quality mono or stereo audio editor, available for under $75 USD.

Grabbing Some Sound

All loops start with some sound you like. For my example, I'm going to use the drum intro to Stevie Wonder's "Superstition." If you already have an .mp3 of this song, you can open it directly into Sound Forge. If you need to record from CD or any other source, hook the sound source to the inputs of your computer's sound card and open the Record dialog by pressing Ctrl-R or clicking the round red "record" button on the toolbar. Check that your recording attributes are 44,100 Hz 16 Bit Stereo or Mono. 44.1/16/Stereo is CD quality, and the Jam Man works with the mono equivalent. Audition the sound you want to capture and make sure the input peaks are between -5 and 0, and that the red "clip" indicators don't go on. To adjust this level, use the windows volume control to control your recording level, or change the levels on your sound source. Click the "Reset" button on the recording dialog to reset the clip and peak indicators.

When you record your sound, don't worry on getting the timing exactly right. As you will see later, we will be able to trim the loop very precisely. So start recording first, then turn on your CD or sound source. Capture as much as you're sure you want, plus a little more, so you have more than you need at each end of the recording, then stop. You should have a sound file that looks like this.

Convert To Mono

Modern music is in stereo, but unfortunately the current version of the JamMan only works with mono audio. So any stereo sound source you start with will need to be converted to mono by combining the left and right channels. This is very easy in Sound Forge: Just right click on the displayed sound and click Properties. The Properties dialog will open. Click the Format tab, go to the Channels drop down and change it from 2 (Stereo) to 1 (Mono). Click the OK button. Sound Forge will ask if you want the left channel, the right channel, or both, which it calls Mix Channels. Usually you will want both.

After you have converted your sound file, the two stereo tracks will be converted to a single track twice as tall on your computer's display. When you play the file, you'll find all the same music, but the stereo separation is gone and all the sound will seem to come from the center.

Setting the Loop Points

This is where Sound Forge really shines, and why you may want to purchase a copy even if you already have an audio editor. In our "Superstition" example, the song starts with a drum pickup to the first measure, and we won't won't those first few beats in the loop. Then the drum intro plays for four measures, but the last few beats of the fourth measure has the clavinet intro to where the other instruments begin to come in. This would sound odd if we included it in the loop, because there would be a few notes of clavinet every few measures, but the rest of the song would never come in. We just want to jam over the drum intro. So of our four-and-a-half measure drum intro, we only have three complete measures of drums only. Since loops are usually an even number of measures, let's loop the second and third measures. Here's how.

Click the Loop Playback button on the transport toolbar to play the file over and over. Click Ctrl-a then Ctrl-home to select all for playback and go to the beginning of the file.

As the file plays, get the feel of the beat, and get your finger ready on the M key.

As you approach the beginning of the second measure, mark the beginning of the loop by pressing M right on the downbeat. You will see a marker appear in the sound file.

Press M again on the downbeat of the fourth measure to mark the end of the loop. Don't worry if you are a little late or early. We'll fine-tune the markers in the next step.

Press the space bar to stop playback.

Press Ctrl-home (go to beginning) then Ctrl-right arrow (go to next marker) to go to your first marker, which should be labeled "1"

Use the up and down arrow keys to zoom in and out of the file. As you zoom in, you'll see that Marker 1 is very near a "bump" in the audio, which is the thump of the kick drum on the downbeat. The actual marker will be slightly before or after the left edge of the bump; we want it exactly at the beginning of the kick. Zoom in until you can see both the marker and the beginning of the kick drum sound, then click and drag the "1" label at the top of the marker line to put it in the right place.

Press Ctrl-Home, Ctrl-RightArrow again to put your cursor on the marker, and zoom in some more. Woops, what looked right at a lower level of zoom isn't quite right when you look more closely. Correct and zoom again. Keep zooming until the zoom level at the lower right corner of the screen reads 1:1 or 2:1, and drag the 1-marker to a point where the line of the sound wave touches the -Inf. line which divides the sound in half horizontally. This is an instance of silence, and you want all your loops to begin and end on points like these. If your loop points are at a non-silent point, you will hear a click at the loop point as the sound suddenly changes levels.

Press Ctrl-End, Ctrl-left arrow to go to marker 2, and repeat the process, setting the 2-mark at the very beginning of the kick drum which marks the downbeat of the first measure *after* your loop.

When you are done, the sound between 1-marker and 2-marker will be two complete measures, and the loop begin and end points will both be at silent moments so there will be no click in the loop

To test your loop, zoom out using the down arrow until you can see both markers, then double click the sound between them. The area between your markers will be selected. Press the space bar to play, and watch and listen as you preview your loop. The rhythm should be even, there should be no partial measures, and the loop point should not click.

Adjust your markers until the loop is perfect. This is hard at first and gets easier. I can set loop points in a piece of music in about 30 seconds, now that I have done it a few dozen times.

When you are done, press Ctrl-C to copy the selected loop and Ctrl-E to paste it to a new file. At this point you can save or close your old file; you don't need it anymore.

Normalizing

In audio editing, "normalizing" means setting the volume of the loudest point in the audio. Volume is measured in decibels, with -Infinity equaling silence and 0 decibels equaling the loudest value the audio file can hold. For drum backing loops, we want the loudest portion of the loop to be between -6 and -4 dB. This is loud but not too loud -- we want room to play rhythm and solo parts over the drum loop without overloading the JamMan.

Again, normalization is Sound Forge is easy. Press Ctrl-Home to move your cursor to the beginning of the sound and ensure you don't have any portion of the sound selected -- if you did have part of the sound selected, the normalization would apply only to the selection, and we want to normalize the entire loop.

Select Process | Normalize from the menu, and move the slider to select -6 or -4 dB. PageUp / PageDown moves the dB setting in larger increments; arrow up/down moves it in hundredths of a dB. Get the level you want and click OK. Your loop's maximum volume will now be set where you want it.

Setting The Length

Now we have a two-measure loop, but that's probably too short to be interesting. You are more likely to want a four-, eight- or sixteen-measure loop to give yourself time to set up some interesting chord changes. No problem! Here's what to do.

Click Ctrl-a to select the entire loop, and Ctrl-c to copy it to the clipboard.

Press Ctrl-end to move to the end of the loop, and press Ctrl-v to paste the loop three more times at the end. You had two measures and just pasted six more, so now you have an eight-measure loop. Press Ctrl-a (set loop region to all) Ctrl-Home (go to beginning) and space bar to play the loop, Make sure the loop playback button is on so you can hear it wrap around to the beginning.

Determining the Tempo

Here's another area where Sound Forge really shines. You will want to know the exact tempo -- not just in BPM (Beats Per Minute), but in hundredths of a BPM. This number will come in handy later when we set up the loop data file on the JamMan. Here's how to use Sound Forge to determine the tempo.

Press Ctrl-Home to ensure you don't have anything selected, then select Special | Edit Tempo from the menu. Make sure the number of beats in a measure is correct (usually 4). Then enter the number of beats in the entire loop in the "Selection length in beats" box. Since this is eight measures of four beats each, I enter 32 here. Press the Tab key and you will move to the Tempo box, and the exact tempo will be highlighted. In case you ever wondered, the intro to Superstition is 97.136 BPM. If you're working through the examples with me on the same song, this number may vary slightly depending on exactly where you set your markers.

Save and Name the File

When you are happy with your finished loop (pretty cool, huh?), save it. Select File | Save from the menu to open the Save dialog.

Make sure the "Save As Type" box reads "Wave (Microsoft) (*.wav)". If it doesn't, drop down the selection and select it. Drop down the Template selector and choose "44,100 Hz, 16 Bit, Mono, PCM". Make sure the "Save metadata with file" is not checked.

I name my files with a descriptive name, followed by the tempo and number of measures. So I would name this loop "SuperstitionDrums_97_8.wav". When I see this filename later, I'll know what it is, how fast, and how long without opening and checking it.

Exploring the JamMan Files

Next, we need to drop your perfect loop onto the JamMan and tell the JM how to use it. Start by plugging in your JamMan and creating a couple loops on the fly. What you loop is not important; we just need to make sure you have some sample files in the JM later. When you are done with the loop, follow the JM process to save the loop permanently.

Connect the JamMan to your computer by hooking up the USB cable. For most Windows machines, the computer will automatically open a folder on the JamMan. If not, you can find it under My Computer as if it were a drive, with a label something like JAMMAN (F:)

Clicking down through this drive (which is actually the Compact Flash memory card inside your JM), you will find a series of directories labeled LOOP01 through LOOP99. There will be one directory for each saved loop on the JamMan. If you have never saved a loop to a particular number, that folder may not exist. Don't worry if there are fewer folders than the number of loops you want to load -- I'll show you how to create new folders.

Click and drag one of the loop folders (like LOOP01) from the JM to your computer's desktop or another open folder representing an area of your hard drive. Sine you are dragging between drives, this will automatically copy.

Double-click the LOOP01 folder in its new location to drill down into the folder. You will see it contains two files, LOOP.WAV and LOOP.XML. LOOP.WAV is whatever loop was stored at that location before. You can double-click this file to hear it play in your default wave file playback software.

The XML file contains instructions that tell the JM how to play the loop. You will need to edit this file to make it match your new loop. Here's how.

Right-click LOOP.XML and select Open with... from the context menu. if Notepad does not show Select Choose Program..., find notepad in the list, and double click it. Make sure the box "Always use the selected program to open this kind of file" box is checked. Once this is done, any time you double-click an XML file it will open in notepad for viewing or editing.

Drag and drop your new loop into the LOOP01 directory. If you right-click-and-drag, Windows will ask you whether you want to move the file or copy it. Select Copy.

Delete the old LOOP.WAV file

Right click your new loop, select Rename, and rename it as LOOP.WAV

Double-click LOOP.XML. The XML file will open in Notepad and will look something like this.

Make sure the value inside the LoopMode brackets is Loop, which must be capitalized as shown (XML is case sensitive). We'll ignore RhythmType and StopMode for now.

If your loop is in 4/4 time, time signature should be 2. Otherwise, change it using the following chart:

0 = 2/4
1 = 3/4
2 = 4/4
3 = 5/4  
4 = 6/4, etc, up to 15/4

Finally, let's set the magic number inside the Tempo brackets. This part gets geeky, but what this number actually represents is samples per beat. The JamMan uses a sampling rate of 44,100 Hz, which means 44,100 samples per second. Tempo is in beats per minute, so we need to calculate samples per minute.

44,100 * 60 = 2,646,000 samples per minute. Our loop is 97.136 Beats Per Minute (BPM), so dividing 2,646,000 by 97.136 will give us the samples per beat. Round to the nearest whole number, so change 27240.1581... to 27240. Put this value between the Tempo brackets.

Press Ctrl-s or select File | Save from the menu to save LOOP.XML.

Go up one level so you can see LOOP01 in the right-hand pane of windows explorer. At this point you can copy or rename this folder to whatever loop number you want to load it to, from 1 to 99. A loop like "Superstition" should be Loop 13, so change the folder name from LOOP01 to LOOP13.

Drag and drop the entire folder to your JamMan.

Unplug the USB cable, connect the JM to an amplifier and speakers, select loop 13, and play. Hey there it is!

Check out the JM's blinking tempo light. Since you determined the exact tempo and set the number correctly in the LOOP.XML file, you will see that the tempo light is blinking in exact time to the loop. If you had not changed this number, it would be blinking in time to whatever the tempo of the previous loop at that location was. Though not required to use the loop, getting the tempo right has a couple advantages -- you can use the blinking light to get the feel of the tempo before starting the loop. You can also reset the tempo on the JM by tapping the Stop button 3 or 4 times to set the new tempo, then storing the loop to the new tempo. This permanently changes the loop inside the JM, so that's one reason you want to copy files to the JM instead of moving them.

Repeat these steps as needed to create as many perfect loops as you want, and move them onto the JM at whatever loop numbers you choose.

But Wait, There's More

Now for a bonus trick. I said before that I didn't like the click track, but here's something neat you can do with it when you are setting your loop's tempo. When editing the LOOP.XML file, set RhythmType to 9. This is tambourine.

When setting the tempo, calculate as shown above, then divide by 2 and round to the nearest whole number. Dividing the tempo number in half doubles the tempo setting. So for the Superstition loop, I would enter 13620 instead of 27240. Now the tempo light is blinking eighth notes instead of quarter notes, and if you turn up the rhythm track, you will have a perfect eighth-note tambourine on top of your original loop. Kinda nice.

Conclusion

The Digitech JamMan is a powerful tool for live looping performance; but unless you want to use the rhythm track, you need nerves of steel, a great sense of timing, and a nimble foot to set the loop points precisely. Pre-recording and loading perfectly looped drum parts in advance makes looping easier and more fun, and lets you concentrate on coming up with great chords and solos to lay on top of your beats. You'll enjoy your loops more, and so will your audience.

Have fun and happy looping!