I discovered this years and years ago and even documented it somewhere in my own notes. Anyway I found it funny to stumble on it again today: Each tune in LN2 provides a tune player as well, meant to be run in direct mode.
At level 1, you can reset the game and type in:
poke 16384,1 : rem this rolls the tune back to the beginning
poke 54296,15 : rem this sets the volume to maximum
sys 17816 : play
To stop, just poke a value of 0 into 16384 🙂