Some of this is going to get number crunchy most probably.

Tune, for the cost of some mana, essentially makes your next song on a given instrument better.

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TUNE
Syntax: tune
tune <instrument>

For especially crucial performances, a bard may carefully tune an instrument
so its sound is perfect for the occasion. A tuned instrument will behave as
if of higher quality the next time it is played, assuming too much time has
not elapsed after the tuning.

If no instrument is specified, the skill will default to the one the bard
is holding.

See also: INSTRUMENTS

Does this increase the song level sung with that instrument or the instrument level itself? Does the level of the instrument even have an affect on song quality (which would follow finding and IDing higher level instruments would be superior instruments even when a lower level one might suit a given repertoire better) Or are you to always use compare without exception and in optimal cases always use the instrument suited to the repertoire you switched to?