No matter the type of music you choose, it should be slow and soft. Choose music that remains around 60 to 80 beats per minute and never rises above a soft volume.
Smooth jazz or soft jazz ballads are effective in helping people to sleep. Music by artists such as Michael Buble or Diana Krall are acceptable.
Some people find gentle folk music to be helpful when trying to fall asleep. Choose folk music that features simple and slow guitar patterns, and soothing vocal lines.
Soft piano music can be helpful to people who have difficulty falling asleep. Try listening to the "Nocturnes" by Frederic Chopin.
Much like music frequently used for meditation or deep thought, soothing vocal music such a Gregorian Chant or soft Renaissance love songs can be helpful in inducing sleep.