So just like other cases in Mabi, such as Ruwai and Rab, you can talk to animal NPCs by logging on your Pet and chatting to them that way.
And the animals at the Arpeggio Concert Hall aren't any different.
They actually comment on some of the recent changes brought by the Fantastic Melody update!
Loafing Cat, mentions Uladh dungeons giving Clear EXP to players clearing them while logged in as a Pet:
I've only done Alby so far, but that gives 150k EXP. Getting carried through Peaca Normal would be a ton of Experience. (And it's only Normal, don't go get carried through Basic difficulty and higher and hope those give completion EXP)
Cotton-Candy-Crazed Raccoon, mentions being able to earn Pet Rebirth Points (PRP) through fighting and music:
Frazzled Cotton Candy Sheep, talks as if they're "baa-ing" certain words, and mentions how you earn Pet Points (PP) every 10th level up:
Carefree Dog, mentions that your pet can get Combat EXP when you play a song all the way through:
Not sure how much, but I tested an "Yvona Renown Grind" scroll from the Bard Board and playing that all the way through gave 12,300 EXP. You can get more if you play a 3+ player Jam Session, but it doesn't really seem that much. And you can't just play forever, what with pet summon time limits. EXP's also based on the Scroll's difficulty rank.
Nibbling Bunny, mentions how a pet doesn't lose any of its previous stats from current level upon rebirthing:
If you rebirth a pet via the PRP system and see it has lost some stats, you're probably just missing stats from its previous Shine of Eweca buff. Shine of Eweca stats don't stay, after all.
You can also talk to the Royal Musician Alliance Maestro, Andante, Largo, Rubato, Lento, and Forte, even though they're not animals, but they don't say anything useful.