That's a great question. I too would like to know.
Exquisite Accompaniment is a nice 3rd level spell that effectively makes it so that you don't expend daily performances to maintain a performance; only to start a new one. I believe you could use it with Virtuoso Performance to maintain two bardic performances for free, until one of the spells wears off. Of course, it'd take 2 rounds to get both spells and performances going, but then you're good to go.
Harmonic Spell is pretty nice, but you might as well just get Extra Performances, unless you cast a lot of spells to make Harmonic Spell more useful.
Virtuoso Performance is an awesome spell, but I'd probably only use it until I can cast 5th level spells at lvl 13 and pick up Shadowbard, and then swap out Virtuoso Performance for a different 4th level spell at lvl 14.
If you're a multiclass Bard, that might not be so easy.
bump
I don't think it works with some secondary performances. It says right in the feat "while you are maintaining a bardic performance" which means only songs you yourself are singing, not spells (like the shadow bard one). But the virtuoso spell specifically says YOU maintain them, which leads me to thinking it would work with that spell, but again reading the feat where it says "a" bardic performance, makes me think just one singular song.
So worst case senario in my mind, use the spell to sing two songs, then use the feat to cover the expensive song?