The Axoloti looks the synth for me http://www.axoloti.com/product/axoloti-core/ a hardware synth (so no pesky shifting sands of a general purpose OS) but is programmable a bit like PureData.
Anyone used one with SPi?
PureData ought to be the one for me, but very few of the massive community of patches actually work sadly. ‘Cannot find…’ ‘Requires blobfinger…’, ‘blobfinger requires zumxam…’ and so on…