just finished this build last night.. can follow up with a full build report, but for now:
here's what i call Principium 3.0.
(still need some slider caps, obviously.)
it's based on some older work i did - info: http://www.psychedelicbabymag.com/2016/08/remork-aka-kris-delacourt.html and https://remork.blogspot.com/search/label/Principium, for those interested.
but essentially it plays back 12 loops continuously, one for each key. so strictly no retriggering: the keys basically control sliders on a mixer, so you get to hear the loop where it happens to be at that point in time. on the left are controls for attack and release times (ranging from 0 to 5+ seconds) and master volume.
while this thing can obviously play back anything you throw at it, for now the basic idea is that each loop consists of a single note, but has several octaves of that note fading in and out. so the first loop is a mix of C1, C2, C3 etc, with different timbres and effects applied so the sound isn't too static.
my first loop is 10 minutes of C's. i pitched that file up to hit the other notes, shortening the loop in the process - the B runs at 5'20" approx. and since they loop continuously, they start to overlap in an unpredictable fashion pretty quickly, so you never quite know what part of the loops you'll get to hear. it's pretty sweet for chordal work, deciding on it's own inversions
it plays back sets of 12 .wavfiles from the SDcard, so you can have multiple sound'banks', indicated by the display.
i'm very much in the process of making new loops, which is a lot of work.. but also a lot of fun, full of anticipation and possibility i'm thinking synth pads, choir samples, strings, the mellotron samples i have lying around, etc.
i actually loaded a test bank with some random songs i had on my hard drive, and it's amazing where you can go with that - so lots of options to try, no need to keep on sticking to the original concept in the long run
back panel, left to right:
+5v power socket, stop/reload button (for being able to pull and edit the SDcard without having to reboot), output jacks, midi channel select button (hold this down, and select ch 1-12 with the keys), 5 pin midi input, speaker outputs.
the panel on the right opens for access to the SD card, there's a USB cable curled up in there to reprogram Bela, and you can access/reprogram the Arduino that drives the display.
that panel doesn't really want to stay closed for now - i used some magnets but they don't seem to cut it. i'll come up with something. and i need those damn slider caps.
also, there's still some options for software upgrades (the whole thing runs on PureData, btw) like a master compressor on the output, and maybe seamless looping (i have a couple ms forced silence now). but i'll be using it as is for now to see what i really need. very happy camper!
oh, and just to be clear: i tried several other platforms, and i DEFINITELY could not have done this without Bela.
so thank you so much for allowing me to bring this thing to life!