I am wondering for a while about how could the music look like...
So here is my thoughts.
The music generally in Faerun could be more important than today, namely more people are versed to make some noise, sound, music in one way or another - simply as not much entertainment exist than today. Also the general background noise of a city should be much different and less, there is no industrialization or combustion engines around.
But the Underdark could be even more specific. Some areas are dead silence, with no vegetation or life (perhaps even no real breathable air), while caverns are full of life but still enclosed space, where the too loud sounds could be a trouble.
Also the different races might enjoy different kind of "music" and has different roles where they use such things.
Here is a few example I am thinking of:
The Drow
They use music both as entertainment, aesthetic form, and religious practices. They are mostly urban dwellers enjoying to live in large communities, so they might consider (generally) the silence as a trouble, something not normal, a source of a danger (a silent cave or tunnel is either not habitable because of lack of air or some hidden predator).
Their music is dominated by singing (especially religious ceremonies), stringed instruments (I think about zither-like instruments designed with the spider-web symbols in mind) where the strings are made from spider-silk, and some wind instruments - like flutes, perhaps pipes.
They might value to the more complex melodies - even improvisation (an influence from the idea of Chaos). They might use none-harmonic elements, I even think they might find scream-like sounds pleasant, perhaps trying to imitate in music (more sadistic priestess might try to use slaves as musical instruments
).
The Duergar
Though the Duergar don't even recognize music as something of a separate cultural entity, they do use music in one for or another without having a word for it. The Duergar enjoy the noises of hard labour in general, the rhythm of anvils, hammers and such. They might define this as a pleasant noise, even separate in language the good rhythm of work from the bad. In some cases they might even use musical instruments, mostly percussions to imitate these sounds and noises to recall a good labour or enhance a work.
The other source of their music might be for the war, moral boosting songs, and drumming. They could even use music in religious ceremony.
The Deep Gnomes
The Deep Gnomes are a careful race, and thus they don't like loud noises and music making where they would give away their location. But they do use music and singing, mostly ones that mimic the nature around them. It is both a practical use and a source of entertainment and communication.