We can make Rock Instruments, but what good are they other than for selling?
Song and dance!
Basically, each kind of instrument can relate to one or more styles, and different dwarves like different styles. E.g, calypso, rock, classical, etc...
There would also be species wide preferences, which cause stronger than normal preferences to various styles of music.
Dancing would raise happiness, and you could build a music stage near your well, or just as a seperate place.
Also:
Artwork. True, carvings on walls can raise the value of an area, but some dwarves should stop to admire it. Some will only admire the same once every once in a long while, but others would frequent various artworks due to strong feelings. That artwork may be made by a dead relative, or depict an event that they were in.
And even more also:
Religion: Dwarves can have deities, but they never seem to worship them. Some deities don't require worship, other than charms (made for a certain deity in the craftsdwarf's shop), and others may require worship at a church. This would make churches a neccessity in the early stages of fortress building. Various religion-neccessary furnitures can be built for the church. Dwarves would be unhappy if they don't have their charms or churches, but they won't get negative effects until after the first year, giving a good amount of time to start building.
Any other ideas or comments?