Building $2 MIDI Instruments for Class Creative Activities
David Brian Williams (david.williams@tech4music.net)
Professor Emeritus of Music Technology, Illinois State University
Copyright © 2003-2007 David Brian Williams (Version 2/5/2007)
Introduction
MIDI celebrated its 20th birthday in 2004; its role has changed since the early 1980’s when its main use for music education was connecting General MIDI music boxes to personal computers.   Now we have superb quality digital audio from our PCs without the need for such external MIDI boxes.  Where MIDI provides a exciting role for the classroom now is facilitating performance with unconventional music instruments for creative activities.
This guide describes a poor-teacher’s approach to building such unconventional instruments. The concept came from the work of Frank Clark (Georgia Tech).  The essentials are as follows:  Wire up some $2 piezo-electric sensors available at any Radio Shack store and turn them into MIDI fun, MIDI triggers pads that students can use in the classroom.  The trigger pads are connected through a trigger-to-MIDI converter to a computer; software on the computer then provides the ability to assign any digital audio file imaginable to any student’s trigger.  The same hardware could be used for simulating an African drum ensemble, an ensemble of traditional Japanese folk instruments, or a rock drum kit by simply assigning new digital music samples to the trigger pads.
Through various experiments with my graduate students and demonstrations, I continue to refine the strategies described here.  If you find this useful and implement the concept, please share your experiences with me along with recordings, photos, or videos you might collect.  If someone finds a cheaper trigger-to-MIDI converter please share that information as well!
Materials
  1. •Radio Shack Piezo Transducers #273-073 (or equivalent), one per instrument
  2. •Audio wire, 2 strand, with 1/4 phone mono plug on one end, bare wire on the other; wire long enough for musicians to stand back away from the computer and MIDI converter,  5-6 feet.
   
 
  1. •Trigger to MIDI converter (e.g., Roland TMC-6) and a MIDI to USB converter (e.g., M-Audio UNO).  A used Alesis DM5 is another possibility.  I picked up a refurb’d TMC-6 from MusiciansFriend for about $150 and I’ve seen them on eBay for a similar price.  [Update 2/5/07: another good option is a new device, the Alesis Trigger IO; $150 and it has USB MIDI thus avoiding the MIDI interface hassles--this has not yet been released but looks promising.  Also check out some DIY (do it yourself) options such as Highly Liquid DIY MIDI trigger circuit (highlyliquid.com) (~$50), www.edrum.info DIY Trigger to MIDI project, and PAIA MIDI Drum Brain for DIY project (~$100).]


  2. •Soldering iron and solder
  3. •Rubber floor mat or whatever you can creatively find that can be cut to shape to protect the sensor, and some super glue.
  4. •Software and digital wave samples (see below)
Building the MIDI Triggers
  1. •Break open the case and carefully remove the Piezo; be careful not to damage the membrane or break the wire leads.
  2. •Carefully solder the leads on the Piezo to the bare wire ends.
  3. •
         
  4. •Cut some rubber squares or circles out of the floor mat material and then glue them around the sensors with super glue.  The goal is to encase the sensor to protect the membrane, but to make it flexible enough so the membrane is sensitive to hand taps or foot stomps.  My students have tried plastic lids as well, but the harder plastic surface didn’t work as well.
  5. •Suggest building 6 of these, one for each of the six inputs on the Roland box.  (Update: 2/5/07: I’ve since discovered that you can use crimp sleeves with a crimping tool to avoid the soldering; I also put a piece of shrink tubing around the connection and applied heat to shrink it. Most any hardware store has these materials.)
Hooking It All Up
  1. •Plug up to six mono, phone plugs into the Roland TMC-6
  2. •Connect the MIDI cable (the one that says To MIDI Output) from the UNO converter to the Roland MIDI port, then the USB cable from the UNO to the computer USB port.
  3. •Settings on the TMC-6: Make sure the switch next to the power cable is in the TRIG 6 position. I used default settings for the TMC-6 beyond this.
Software Options
You need software that makes it very easy to assign MIDI control codes to digital wave samples. Abelton Live is the first software solution I worked with for these projects.  You can set it to MIDI mapping mode and then tap one of these sensors to assign it to any cell in the Live matrix; it is very easy to do.  Live is not inexpensive however; about $250 from academicsuperstore.com.  Live may also be more complex than needed for this activity. (update 2/5/07: M-Audio ships Ableton Live Lite free with their digital audio hardware; I’ve now used this and it works great for this project.)
Another solution I’ve found is software called Alphabet Soup from OZmusicCode.com ($60 to download and license directly from their website). Here is a brief walk through of how I set up both of these.
Ableton Live.  Run the application Live and set it to the Session Chooser mode where you see basically a spreadsheet or a matrix: the columns are Tracks and the rows are Scenes.  Notice the cells in the screenshot of Live above.  From the file browser to the left of this spreadsheet drag any WAV sound into any cell (this could be a single shot sound or tone to an entire music track from a CD--anything!).
Now you need to map your piezo MIDI trigger pads to the the cells, one trigger for each cell that contains a digital audio clip.  Click on the MIDI map mode switch in the upper right-hand corner as shown to the left.  Make sure your MIDI input is working.  Just tap on one of the trigger pads and you should see the MIDI map button blink.
Now selected a cell like the purple Rhythmic clip shown on the right below; then tap one of the trigger pads.  The MIDI controller number should appear like 10/D3 shown on the left below (notice that the entire matrix is purple when in MIDI mapping mode).  The “10” is for MIDI Channel 10, typical channel for percussion; the “D3” is the note number assigned by the TMC-6 for that trigger input. It is possible to change this assignment by digging into the TMC-6 manual. Select other cells and then tap a different trigger pad attached to the TMC-6 to map that trigger to another one of the Live cells.
When done, deselect the MIDI button and then start playing the trig
ger pads.  Each one should trigger a different cell in the matrix.  Change out the sounds and try something different; experiment with how you can create Scenes of sound where the trigger causes a sequence to play. Live is self-documenting so just click around and see how things work; when you hold your cursor over a feature the documentation appears in the lower left corner.
Alphabet Soup
Alphabet Soup gives you a graphic of the keyboard (in the preferences you can choose different vegetable color).  Each set up of sounds is called a “soup bowl” of sounds.  Drag any WAV file from the desktop onto any key; a white dot will appear to indicate there is a sound attached.  
In the figure above, three WAV files have been attached to the A-key (Anxiety), the F-key (Bryan’s Dream), and the X-kay (Ebase A0).  To assign one of the Piezo trigger pads to a key, right-click on the key and a window will appear as shown.
Click on the “Learn MIDI” button and then tap the trigger pad and, like in Live above, the MIDI channel and key should automatically be assigned. Now close the window; set a different trigger pad to the other sounds; then tap away!  This is a much simpler interface to work with for beginning projects.
 
Demos
Here are two QuickTime video clips showing this project in action.  





The first is a short clip working with some middle school children who had little to no involvement with music in their school (This was a project done by my student, Justin Routh).  The second is a clip of music teachers in the CMS Music Institute lusing the sensors, a TMC-6, and a Mac PowerBook with Live (and a MIDI keyboard).  You can see the Live matrix projected on the wall and the various cells being triggered as they played.