Interesting project, pointed out by someone on the lines community....
http://zynthian.org
Basically an open source platform based on PI2/3 +HIFiBerry DAC+ LCD and some knobs...
then a collection of software they are integrating....
(It seems to be hackable project, i.e. i don't think you can buy one, not sure if that is in their plans or not)
Its not a modular like, Axoloti, rather a packing of a PI in a musical format, including synths/samplers etc.
It could be nice to see a modified distribution you could use a PI out of the box for this kind of thing.
so far doesn't look like any big kernel changes, so not using a real-time kernel, and latency is quite high, boot up times 'ok'.
as I have a PI2 + HIFIBerry knocking around, I might give it a go... I've actually also ordered some pots to, so perhaps just need a display and I'll have 90% of the components 
as I said, not really like Axoloti, which is provides a modular, low latency building your own synth platform.
on reflection, I think its probably more a competitor to C&G Organelle, ok Organelle has a keyboard... but mini keys are cheap... also it uses PD, but that would be pretty simple to add to this.
anyway I thought it was interesting