Instrument skills?

[FinalPhantasy13]

I'm sorry if this has already been answered but I really had no idea what I oculd use for a search on this one. My question is: How do your skills with the wind and string instruments effect your songs? Do they shorten cast time, make them last longer, or make them more effective? Thanks in advance!

[DuoKisei]

From what I've seen, the only difference I know is that string instruments tend to have a much, much larger radius of effect than wind instruments do, which can be a good or bad thing depending on what you want to do.

[Rekiem]

Your instruments skill make your songs more powerfull.