Music in Galaxy is one of the highlights of the game. This page lists the current songs in the Galaxy Soundtrack.
Music in Galaxy is usually played randomly, however the music is split up into 3 categories. Peaceful, Combat, and Other. The game alternates between these 3 soundtracks depending on your situation. The Peaceful Soundtrack plays when you are not in combat (e.g. mining). The Combat Soundtrack plays when you are in combat (e.g. getting attacked by other players). The Other Soundtrack is usually played during certain events or in other situations, this category is very versatile and has a wide variety of applications.
When Roblox implemented a privacy system into the audio catalog for the platform, a lot of songs used for Galaxy were privated and unable to be used in the game. The Development team prepared for the update beforehand and decided to have rcouret reupload all of the Galaxy Songs under his account so that they could be used in Galaxy. While it did work, and it saved a lot of songs from being unusable in Galaxy, it means that most, if not all, of the links to the audio's roblox page will be unplayable. You will probably have to use the reuploads found on the Galaxypedia instead.