Is this the forum you meant to ask this on?

But two things:

you're trying to use the output audio before you've closed the write handle so maybe the file isn't fully written yet

you run "start output.mp3" but will that find "/tmp/output.mp3" which is what you wrote? I suspect the working directory is not currently /tmp. So try "start /tmp/output.mp3" as well?

Or find a Python library which plays MP3s and use that.

And definitely check that the output.mp3 does get written and can be played with a normal MP3 player.

Thanks that's great! It seems to work fine using a 3.5mm stereo - 2x 6.5mm mono cable with just one of the mono end plugged in. On a Link I'd be using the line out so wouldn't have these concerns - I suspect I will get a Link at some point, but only if the opportunity for live performance arises I think. Or I start wanting those MIDI ports...

I haven't been able to find anything in the Slyphyo's technical information about what the headphone jack actually is - specifically is it stereo? Does the synth output stereo data or can I just take one channel of it and feed it to a mono input?

I'm wanting to use the Slyphyo without a Link initially, so I would like to have a better idea of the nature of the sound output. If I get really serious I will of course get a Link and take advantage of its line output.