Midi Billow is a 5 button, six note, mellotron in a portable cassette player. Unlike billow, it has a midi input to control motor speed. The two modes are exclusive. The midi mode can ONLY be used with loop tapes. Midi mode eats long play tapes :) The midi control is implemented in python to make it easy for beginners to play about. The player can also be used as a normal cassette player. See and hear some examples at https://poetaster.org/midi-billow

The design files and code are in Fritzing/python and can be downloaded at https://github.com/poetaster/billow

Also features:

1. Headphone output
2. FM/AM radio (yeah!)
3. battery power with two AA batteries
4. comes with a usb adapter to power of a normal 5 volt phone charger.
5. works with most tape loop tapes, though not always a and b sides.
6. Program via usb-C and circuit python

I designed midi Billow so that the simple resistor based motor control works exactly as in the original. So, 5/6 tones just on the buttons. The lowest right small switch controls if a 'default' speed is set. That then limits you to 5 notes. But you can set the speed for 'normal' play.

The picture with numbers shows:

1. headphone output
2. mode selector (midi/buttons)
3. usb input rp2040 zero
4. 3.5 mm midi input
5. 5v on off for the rp2040 when 9 plugged 6 range selector in button mode to set the ‘default speed’ with the final pot
6. speed pots
7. buttons :)

The midi input is via a 3.5 mm jack/adapter controls an LH9110 which sets the voltage to the motor. This requires using the 5volt input on the billow to get anything like decent range. The second small switch turns 5 volt to the pico on and off.

The waveshare pi 2040 zero, used for it’s size is programmed with circuitpython to make it fast and easy to iterate changes. You can plug it in and directly change code while playing it.

The range, given the motor, is limited. If you tune microtonal, 24 intervals, not log, so microtonal. In practice I find 13-14 usable intervals. If you try to tune it to notes, max 8 notes. But default, it’s setup so midi notes 49 - 63 are equal divisions and 64-74 are log ‘musical’ divisions. This is probably all you ever need ;) but, one can 'fine tune'.

Also, the ’normal’ resistor button control works fine with long play tapes. But, using midi and slowing down ‘so’ much and speeding up so much means that it’s only usable with tape loops. Midi mode EATS long play tapes.

I usually add some monster decals and a bit of decoration, but if you let me know I'll send you one without monster deco :)