When it's off, and it's quiet, hood up, I can hear what sounds like a little techno song coming from the driver side of the engine compartment. It's too quiet to really even record, and I can't find the source. It's a rapid beeping, maybe 250bpm, and there are 4 notes that are different, and repeat in a 4/4 time.
It's always there, even when I walk out the next morning.

Go listen to your rover, does it sing to you too? Around / under the throttle plate.
What is it?

 

I sing to my Rover, not the other way around

 

Its probably the ABS pump. Mine sings some too. More of a buzz though on mine.

 

It's more of an old school techno tune introduction. Or a 80's video game alien spaceship sound effect.

It's the Wabco abs thingy. Mine does it. Think they all might.

Everyone seems to agree it isn't a battery drain.

Mine sits for weeks at a time and doesn't suffer a battery drain. [touches wood]

 

My SAI pump buzzes if I run the engine for less than a minute or so and then shut it off, but only after a cold start. I guess that's borderline musical.

I wonder if I fixed my 3 amigos if my ABS would sing too. I would love for my disco to sing to me as long as it didn't point to another thingbreaking