As far as I know (and please do correct me if I'm wrong), we never get to see Rocky reacting to human music (or vice versa), and I haven't seen any posts about it, so it's headcanon time
Assuming that Eridian language is entirely tonal/rhythm-based (how would they even make consonants or varied vowels), and each pitch/chord that they can make represents a different character/concept (I'm imagining something like Eastern languages here, where there are concepts built upon concepts by combining characters/chords?), I think that Rocky would find human music kind of nonsensical. In songs with lyrics, I'm sure he could understand them, assuming they were sung clearly enough, but the changing tones and instrumental chords and such would have him catching snippets of Eridian concepts/chords/rhythms that aren't there in whatever human language it was written in.
"Why song about love keep using Eridian word for table, question?" etc
As for whether or not he'd like it, that's anyone's guess. I like to think it's not his favorite at first, but he warms up to it over time.
I don't know how Grace would feel about Eridian music. Imagining their language as tonal means that most (if not all) of their music would be inherently lyrical (since music is essentially notes and rhythms strung together, which is also the basis of their language itself), so I'm imagining that a lot of their songs/lyrics are written specifically in ways that make the words sound good together, both in meaning and actual sound
That being said, the chords and rhythms that sound good to humans may be very different from the chords and rhythms that sound good to humans, so who knows whether or not Grace would like it
I also like to think that Rocky starts Grace out with a bunch of baby songs meant for teaching baby Eridians their language
Additional note: Eridians can hear higher and lower frequencies than humans, and I'm sure their music would utilize most of those frequencies, so I'm sure there's a lot of Eridian music that Grace just. can't hear
"Best part soon, listen, Grace"
"??? ...Can't hear it, Rock"
"Oh. Too low sound for human ears. Sad" (He continues bopping along to the music sadly)
I also have a feeling that a good number of Eridian songwriters would also start creating "human-friendly songs" specifically for Grace, i.e. songs that only use pitches that he can hear, and mostly simple words that he knows/likely knows
Of course, this is all only my opinion, feel free to let me hear yours!










