Trying to force a specific song length other than the default never quite worked, so we'll only support the default MAX_SAMPLES & will calculate it for the user in the user in the exported .h header file.
Whoever uses it, probably wants their own Patch format, as now it is pretty cumbersome to work with sampleoffsets and delays, as the user needs to construct the delaytimes tables and sampleoffset tables.
TBD: should the various []bytes be marshaled in a different way? Go defaults to base64-encoded strings but creating just plain JSON arrays with bytes could be more friendly to both humans and computers.
