One of my favorite combos is with AA *and* Grandpa Legacy. If you have AA's instruments/songs set up so that he can use multiple Performs/Accompanies on a turn, then Grandpa Legacy can use his Gung Ho! power to let AA (essentially) have another go at it while healing in the bargain. Here's an example of what I'm talking about:
AA has:
Alacritous Subdominant
Inspiring Supertonic
Inventive Preparation
Telamon's Lute (Harmony Perform and Rhythm Accompany)
Musaragni's Harp (Harmony Perform and Harmony Accompany)
AA's turn:
(1) Musaragni's Harp -- gives him a Harmony Perform and a Harmony Accompany:
(a) Harmony Perform -- use Inspiring Supertonic's Perform which lets any hero use a power. Use that on AA; it will let him play another instrument...
(i) Telamon's Lute -- gives him a Harmony Perform and a Rhythm Accompany;
(A) Harmony Perform -- use Alacritous Subdominant -- any hero can play a card out of turn (**Note: If you've been spamming this for a while, and you don't need as many out-of-turn card plays, then swap this for a second Inspiring Supertonic, and let a hero use a power out of turn)
(B) Rhythm Accompany -- use Inventive Preparation -- any hero (except AA) can play a card out of turn
(b) Harmony Accompany (from Musaragni's Harp) -- AA gains +2 HP (I find this particularly useful, since AA is often the hero with the least HP, and tends to get beat on often)
So at the end of AA's turn, you've had two out-of-turn card plays, and AA has gained +2 HP. Then if Grandpa Legacy is next, have him use Gung Ho on AA to let AA use a power out of turn. As the power, use Musaragni's Harp, and repeat the steps above. After two hero turns, the end result is *four* (4) out-of-turn card plays, and AA gains +5 HP. With four out-of-turn card plays, suddenly setup-heavy characters like Unity, Fixer, and Expatriette become much more workable. Or RA/Tempest/Tachyon pound enemies to hamburger with strings of damage one-shots. Or combine this with characters who have one-shots that allow out-of-turn card draw/play (Tachyon, Scholar), and you can add still more out-of-turn carnage.