What tunes can you play from the sound system?

Question

I was checking out my cabin aboard the Normandy when I discovered a wicked sound system just waiting to be cranked to up 11. I flipped on the power switch and a mediocre techno jam streamed out, eliciting a ho-hum reaction from my ears.

Leaning in for a closer look, I soon realized that the track, volume, and AM/FM/XYZM radio buttons were all just stickers applied on the front of this so-called "sound system"! With a sigh, I opened up the owner's manual and found it exclusively written in asari, volus, and Chinese. Stupid budget cutbacks!

What music can I play from the sound system in my cabin, and is there a way to choose what song I want to listen to?

Answer 1

From the page on the Normandy SR-2 on Wikia:

Aside from a full-sized bed, bathroom, office desk, and standard furniture, the Captain's Cabin features a display case for tracking the progress on Achievements, a private terminal for monitoring basic information about squadmates, reading new and archived emails, and viewing advanced training videos, an armor locker for modifying Shepard's casual attire and combat armor layout, and a sound system that can play tracks from the Mass Effect soundtrack.

So yes, you can only play songs from the Mass Effect 3 soundtrack, and the sounds are selected at random. The Mass Effect 3 Soundtrack was composed by Sascha Dikiciyan & Cris Velasco. All the songs are pretty good, but the only option you have is to turn them on or off. At the time of the writing of this answer, the Soundtrack is available only through purchase of the Mass Effect 3 N7 Collector's Edition or Digital Deluxe Edition.

Answer 2

You can play most songs from the soundtrack, and to my knowledge the selection is random.