I remember in some interview that Rand and Robyn Miller originally didn't want to have music in their games because they thought it would disrupt the gameplay. And once Robyn started dinking around with a synthesizer he felt that what he experimented with actually provided some additional ambience to the game.lacktheknack said:Myst in general did their music really well.
That being said, there are some exceptions I would make to the series. While not an original Cyan Worlds game, Myst 4 Revelations was alright but it had the very first Myst track to include vocals. The dream-spirit deal with the singing was a pretty big scratch in the record for a decent game.
Myst 3 Exile had good music, but like the original Myst they were too short in length. Especially the intro musics that play whenever you get to a new age. Voltaic and Amateria's theme were my absolute favorites out of that game, but they were too short! They're a minute and a half long.
EDITED:
Whoops.... Exile was the first to include vocals with their chorus singing in a crescendo all the time. But Revelations had vocals that were discernible to the ear, and you could make out the lyrics.