Was tying note offs to ons in run recording to save space, but this loses the ordering info which is more important. It could be possible to recover the order using the score, but it is hard, and if playback is affected by noteoffs in future this would break.

Adding full info for noteoff serialisation. Solves hassles with bad links between note ons and offs (though this was a good checksum mechanism). Makes code more simple too.

The session can contain the user to score settings (saved when the first run begins) and each run saves settings diff at the beginning. Run also saves a time diff (in seconds will do).

It really should be a session that links a user to a score, with settings linked to a session. Too much work to change now though. Current design manages the 'current' (latest) settings better anyway without needing another table.