MIDI and the Accordion

MIDI stands for Musical Instrument Digital Interface. It uses digital signals to play notes and select voices. MIDI pickups on an accordion do not transmit the accordion sound. They are systems of electrical switches that feed into computer chips which generate MIDI messages. These messages feed into sythesizers which produce the musical sounds. The sounds that come out are usually not accordion sounds.

A MIDI message will instruct the system to turn a certain note on or off. It will tell how hard to attack the note using a number to indicate velocity. Some of the more expensive systems will read attack velocity in the instrument and transmit the code. Less expensive systems use a pre-programmed velocity number. MIDI messages also transmit program changes. Typically a program change would select a voice. MIDI messages are transmitted one at a time over a serial cable. Each one takes a certain amount of time, but things happen so quickly that it seems instantaneous.

MIDI gives an accordionist a choice of voices. It offers the opportunity to add a piano, trumpet, or even drums, to the accordion sound. A piano accordion can be played with MIDI but without the accordion voice by not moving the bellows. A diatonic accordion must have air movement to actuate the push-pull switch, so the MIDI sound will come along with the accordion sound.

General MIDI is a standard set of values for MIDI messages. Thus a particular voice will always have the same number no matter which General MIDI instrument is in use. There are many sythesizers which are not General MIDI. They frequently produce voices which are not included in General MIDI.

Adding MIDI to an accordion can be expensive. The hardware for a retrofit is expensive, and it takes a lot of labor. Typically, MIDI will be added to an instrument which is already expensive. The fancier conversions use magnets which trigger the flow of current through transistors instead of using switches which make physical contact.

It's possible to build a MIDI accordion for not much money. Tom Scarff of Dublin (see links) has interesting circuit boards for sale. His MIDI melodeon (diatonic accordion) circuit boards are stocked in D-G and B-C tunings, but he will do custom programming for other key arrangements. It takes more parts and some work to make one of these boards into an instrument. I purchased one of his B-C boards and built an instrument around it. I bought some computer keyboard switches and some switching diodes and built a housing from some two-inch cedar I had in my shop. It cost me less than $100. It feeds a signal to my Yamaha PSR-280 keyboard.

The home-made MIDI box works well, but it plays the keyboard only with the default piano voice. Tom has not yet got around to marketing a board which will select the voices. There are voice-change units on the market but they are very expensive. The voicing and transposition controls of the keyboard do not operate on the MIDI signal.

The instrument is very tricky to play. The computer switches I used are much more sensitive than accordion valves, and the system is always on either the push or the pull with no allowance for a stationary bellows.

In building the instrument, I found that the switching diodes are very fragile, and if one breaks, the key to which it is attached won't sound. I also found that switches available in bulk are not always completely reliable. Some of them might be a little balky and will need to be replaced during testing. The electronics hook-up is not difficult, but building the housing and installing the subassemblies requires some planning. One feature of Tom's board which I like a lot is that it has solderless screw terminals. These are the best I have ever seen on a circuit board.

Tom has another board which might work better, but I haven't tried it. This is a pitch to MIDI board. It receives audio from a microphone preamplifier and puts out a MIDI signal for the pitch it hears.

Some final words of caution. As noted above, the controls of a keyboard will likely not work when it is fed with an external MIDI signal. MIDI controllers are expensive. Also, professional MIDI installations are very expensive. Unless a MIDI system has a center off position on its sensing switch, it will be quite a challenge to play. I think MIDI would work much better on a piano accordion than on a diatonic button accordion.