In audacity why does the music play when it is not in recording mode but when it is in recording mode you can hear vocals but no music?

In Audacity, when you're in recording mode, it typically mutes playback of existing tracks to prevent feedback and ensure that the new vocals are recorded without interference. This allows you to focus on your vocal performance without the distraction of the music track playing back. If you want to hear the music while recording, you can enable "Software Playthrough" in the preferences, but this might introduce latency.