Yeah I just watched a video on HH, looks dope. May have to give it a shot.
How hard is it to wrap your head around all the music/buff stuff? I'm not a master at this series by any means
It's simple memorization and has nothing to do with being familiar with the series, unless I'm missing something. Are you not actually playing yet?
The amount of songs each HH has varies. Could be anywhere from 3-6, and each one requires a specific order of musical notes to play (You'll see these notes on the top left. When you have a playable song on the staff, the notes and staff will get highlighted).
Each "note" is tied to an attack (X, X+Y, B), so in order to play a song, you need be mindful of how you attack. And be aware that "playing" a song is also an attack (but not counted as a note)! Study the songs, get a feel for your attacks' timing, and just survive like with any other weapon against a big monster. Missions are long, so once you get in one, stay in zone 1 and just practice what I said above. It's clunky, but you can check your songs if you need to by pausing and going to your equipment/status section. I forget off-hand the exact place.
As for the buffs, you'll have to keep an eye on them and reapply them when needed. They'll show up as icons next to the party's names. You can also apply a stronger buff by playing the song again, or simply doing an "encore" by hitting R again, which is how you "play" songs. But it all depends on your situation. Obviously you don't want to encore in front of a monster's charge.
You'll soon learn that you're not going to be playing a song every second. You have to balance attacking with purpose in order to play a song and attacking with purpose to just beat the shit out of a monster.