I have never used a micro-controller for anything, but I am a proficient builder of electronic and mechanical devices.
I am hoping to build a “Band in a box” machine that will be capable of playing instruments I build. I am hoping to make several octaves of air powered whistles and some percussion to play tunes. I will be using 12V DC valves and solenoids to do the work. I am looking for the best base board to accomplish this and the best way to load or select different song files. I see MIDI shields but these seem setup to control devices that already communicate with MIDI. Here is a link to a percussion project, but it does not explain the hardware used.
A lot depends on how many instruments you intend to control and the interface to each instrument. This is why a standard like MIDI exists. No controller could anticipate all the instruments and all their particular interface needs. The onus is then on each instrument to conform to a standard interface for wiring and data protocol.
If you only need 11 I/O pins, a Uno will suffice. If you need 4x that, perhaps a Mega. If you need even more, you might be back to an Uno and a shield or 3. If each pin needs to source or sink > 40 mA (to drive a solenoid) you may be best off w/an Uno and a power driver shield of some sort (only because there are more ‘Uno shields’ than there are ‘Mega shields’).
Actually, if you want to be able to load control files, I’d go with a Raspberry Pi. Sure, you can load files from an SD card on an Arduino, but this is a case where having an OS to do the heavy lifting will make things easier. Also, the cost difference between the Pi and an Arduino will be lost in the noise. You’re going to have so many expensive mechanical parts, that an extra $20 won’t be noticed. It will, however, pay for itself in being easier to program.