Given his druthers, my son will listen to pop music. Pop music, and the theme songs to TV shows. He basically uses Netflix Instance as a jukebox, playing the first 30 seconds of a variety of programs just to hear the intros, or jumping around Curious George 2: Follow That Monkey to find the musical sequences.
We usually have the car radio tuned to C89 FM during our drives. But music has a noticeable affect on him: fast songs wind him up, slower tunes calm him down. So when I put him to bed I let him select a playlist from a curated collection, one confined to albums with soporific qualities. This has worked wonders in getting him to sleep. Before he could be up for hours, rolling around in bed, kicking the wall, laughing and whooping; now he listens to music with such an intensity and stillness and he usually drops of to sleep within minutes.
His favorite album is The Kaleidoscope by a local duet called Lemolo, a perfect blend of the eletronica and lilting female voices that he prefers. We carry Kaleidoscope with us on our phones, and even have a CD in the car, ready to deploy in case of meltdown, with the self-titled album by The Lumineers as an emergency back up.
Here is a playlist of songs, taken from my son’s favorite “going to sleep” albums.