system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5 how do people isolate specific audio tracks from a file without access to the master tapes? Such as when someone makes an isolated vocal or bass track of a song or when someone makes a mashup of instruments from one song with the vocals from another.

Such as when people make "isolated bass/vocal," tracks of popular songs or make a meme mashup of one song with he vocal line of another over it?
gpt
To add to what the other commenter said, audio files are usually in stereo - there are actually 2 tracks, one for the left side and one for the right - and when a song is created, different sounds are usually placed in different locations in the stereo field. Lead vocals, kick drums, bass, and sometimes snare drums are usually placed in mono - the left and right channels are identical. Most other sounds are usually not in mono - the left and right channels are different. For example, a sound may be panned, where the volume on one side is louder than the other.

If your goal is to extract vocals, you can simply discard all the data that isn't the same on both the left and right channels. You will be left with less overlapping frequency information to try and cut the vocals out of.

There are also AI tools that can assist with separating tracks, such as Spleeter.