This page is to document my experiments making a bellows-less electronic melodeon.
When I started thinking about this project I was intending to adapt an existing junk box with my own MIDI electronics. Ostensibly this is to allow me to play in different keys and to practice silently. But really, its just for the fun of the challenge. Either way it soon occurred to me that it would be fun to try to make something small and portable and from there it wasn't much of a leap to think that bellows probably weren't required. When I mentioned this idea over at Melodeon.net someone pointed to some prior art in the form of a bellows-less concertina. This gave me a little bit of confidence that it might actually be playable when complete.
For my first attempt I used a small wooden box found in a charity shop. The two parts of the box were re-arranged to form the bass and treble ends of the instrument. A small pressure sensor is fitted in the joining mechanism between the two halves. The sensor can tell how much pressure is being applied to push the two halves together or pull them apart.
The buttons are standard momentary push buttons purchased from Rapid Electronics. Some additional buttons and LEDs are provided on the back to perform control functions such as key change and voice changes and indicate which settings are in effect. The buttons are somewhat programmable to allow layout changes, key changes, MIDI program changes etc. to be assigned to any button.
The instrument connects to a computer via a USB cable and appears as a MIDI port on the computer. Any MIDI synthesis / sampling software can then be used to produce sound output. Internally a PIC18F4550 Microcontroller reads the buttons presses and pressure information and send the correct MIDI signals to the computer.
So, is it playable? Well sort of... (click/touch to load YouTube video)
As can be seen from the video, it is possible to get a tune out of it. But it is rather hard to play for a few reasons:
- The buttons are much too stiff - you have to push them very hard. Coupled with the fact that it responds very quickly to "bellows" changes, this means you have to really mash the buttons whilst at the same time using a light touch with the push-pull. Also because it's quite small it's quite difficult to hold it still whilst pressing the buttons so hard.
- The bass buttons are in the wrong place. I put them in the position they would be on a full size box. However this makes it hard to hold the instrument. It soon because apparent that the buttons need to be a distance away from the bass end to allow your palm to hold the end of the instrument, with the strap across the back of the hand as on a full size box. The way it is now the strap is across my fingers when playing and this means that my fingers can't move easily and it is hard to hold onto it.
So I will probably make a mark 2 with better buttons and a different bass position. I think there will be a couple of other changes:
- Make it slightly bigger to allow for a few extra treble buttons and slightly larger button spacing.
- In mark 1 I used only one pressure sensor and tried to pre-pressurise it so that I could measure pull and push with one sensor. This is rather unreliable and means that accurate pressure sensing is hard. I should probably just get another sensor and have one for push and one for pull. This will allow me to have bellow pressure control volume in a more realistic way.
Other things I would like to try:
- On board synthesis with battery power and headphone socket.
- Making some kind of custom casing or fitting the electronics into a full sized box with an air pressure sensor.
March 2011