I’ve been working on an idea for a Eurorack module to use with my X0x Heart.
Connect up a MIDI synth (or use a VST/AU in some software host) and see what you think.
Note: the MID-file recording feature isn’t working yet.
It uses Web MIDI, which is only currently natively implemented in recent-ish versions of Chrome. You will need to install the Jazz MIDI plugin, to use the page in other browsers, unfortunately. I hope Web MIDI will be natively supported in other major browsers soon (but suspect it’s not a big priority for developers, sadly).