'M' should mute / unmute the audio, including the music for this particular game XD. I thought that might be an issue this time...
I added the music quite late, so I did the absolute minimum on it and just never thought to go back to patch it. So it's very short, and in some sense missing a melody, so it doesn't have the variation it needs. I'm quite unhappy that the music is so lacking this time but I was more focused on visual elements for this game.
So yeah, feel free to mute it XD.