At first, the game wasn’t meant to have any music at all, because its creators feared that it would detract players from the puzzle solving. However, they realised that it did help to create an atmosphere in some places, and so, some locations have background music, like the planetarium on Myst or the fortress on Mechanical. The tracks aren’t particularly long or elaborate, but they are genuinely effective and fit their respective locales to a tee. There’s an overall prevalence of strings and reed pipes, resulting in a somewhat surreal and melancholy general atmosphere. Every age has its own theme, which you’ll hear upon entering the room where the relevant linking book is kept and/or the room where the book back to Myst is located.
Selenitic’s theme (“Selenitic Mystgate”) is the most elusive, as you only hear it in the latter area. This is probably due to the fact that the linking book to Selenitic isn’t actually physically accessible. Be that as it may, the theme is a slow, minimalistic reed pipe sequence, both lonesome and eerie at the same time, just like the age itself. Channelwood’s theme (“Treegate”) is only heard when accessing its linking book and consists of an odd mix of piano and bongo, for that tribal feel. Mechanical actually has two themes: one which sounds like a clockwork mechanism, heard when you first access the linking book (“Geargate”), and a more musical one, albeit still with metallic sonorities, heard when you locate the book back to Myst (“Mechanical Mystgate”), which is a variation on the ambient music heard inside the fortress. Stoneship’s theme actually sounds like a cloudy sky before a rainstorm, with its moody oboe-like main sequence and its rumbling undertones (“Shipgate”). There’s also a second leitmotif associated with the age, which can notably be heard near the spyglass and consists of another eerily lonesome reed pipe sequence (“Above Stoneship”). In realMyst, Rime gets its own, frosty-sounding theme (“Rime Mystgate”), as well as an additional, surprisingly urgent and elaborate theme inside the crystal viewer room (“Rime Crystal Chamber”).
Myst island also has its own theme, which can notably be heard at the beginning of the game. It also creates musical coherence throughout the game. You see, Sirrus and Achenar each have their own theme as well, but they’re actually elements from the main Myst theme taken to stand on their own. The former is a furtive string score, while the latter is an ominous ambience. These themes can be heard in the brothers’ respective quarters in each age, with a slightly different arrangement to incorporate each age’s own musical theme. For example, on Stoneship, they inherit the main theme’s background thunder-like rumbling. On Mechanical, they have metallic sonorities, and on Channelwood, they include some bongo. This is a clever move, as it clearly establishes that the fates of Myst island and its ages are inextricably connected to those of the brothers.