Western music became much more rich when we moved from simple, monophonic Gregorian chants to multiple lines of melody (polyphony), allowing interplay among the different lines. Nowadays Gregorian chants are still admired by more traditionalist Catholics and Middle Age junkies, and if you listen to a Gregorian Chant channel on Spotify it’s kind of interesting for a little bit, but I’m not holding my breath that it’s going to be competing with Taylor Swift anytime soon; by any standard adding harmony almost always makes music better by allowing a more sophisticated and richer interplay of point, counterpoint, rhythm, timbre, tone, and so forth (here and elsewhere, I think I’m using the terms right. I dropped out of AP Music after a week). 

However, research suggests that as you add more lines of harmony or voices our ability to discern individual lines deteriorates; streams of melodies start to integrate, and different facets of the music come to the surface depending on which ones we’re focusing on. (Anybody that’s focused on just a baseline or this or that in a song can attest to the fact that a song delivers a different experience depending on where your focus is). 

However, God presumably has no such restrictions on attention span, so here I’m going to play with some possibilities for what music would look like when we’re not subject to mortal restrictions (similar to what I did with color and art a while back). While at some point too many lines of melody mush together and integrate or become discordant, in principle a divine being who has no restrictions on thinking multiple thoughts at once could experience and enjoy more than the 3-4 lines of melody that humans can holistically experience. In principle I suppose, a God can enjoy dozens, hundreds, thousands of melodies that retain some discrete, distinct role in the polyphonic whole without devolving into mush, and can fully and completely enjoy and hold each line at once while also taking in how it interplays with the other hundreds of lines harmonically, melodically, and rhythmically. 

In principle our AI and musicology might advance to the point where an algorithm could generate such a song that, even though it would sound like mush to us, would be beautiful if heard by the kind of being who could absorb exponentially more lines of melody than we could. 

Finally, and this is more speculative, but maybe some aspects of music like, say, pitch that we see as being one dimensional, could in some sense be fundamentally two-dimensional. In the same way that some physicists posit a second dimension of time that we are unaware of and incapable of experiencing, so too maybe there are more possible dimensions of musicological variables that can only be grasped by a superior being, exponentially multiplying the possibility and richness of the ultimate Celestial choir or orchestra. 

P.S. I’m adding this long after the OP, but for the record I ran across a quote about polyphony (after it was invented more or less at Notre Dame Cathedral in Paris) that is relevant.

Bad taste has, however, degraded even religious worship, bringing into the presence of God, into the recesses of the sanctuary a kind of luxurious and lascivious singing, full of ostentation, which with female modulation astonishes and enervates the souls of the hearers. When you hear the soft harmonies of the various singers, some taking high and others low parts, some singing in advance, some following in the rear, others with pauses and interludes, you would think yourself listening to a concert of sirens rather than men, and wonder at the powers of voices … whatever is most tuneful among birds, could not equal. Such is the facility of running up and down the scale; so wonderful the shortening or multiplying of notes, the repetition of the phrases, or their emphatic utterance: the treble and shrill notes are so mingled with tenor and bass, that the ears lost their power of judging. When this goes to excess it is more fitted to excite lust than devotion; but if it is kept in the limits of moderation, it drives away care from the soul and the solicitudes of life, confers joy and peace and exultation in God, and transports the soul to the society of angels.