I love these. Very good for background music, and they're repetitious, which works for me.
My wife, however, is a classical/jazz musician, so she can't use music to focus, it causes her anxiety because she spends time analyzing the music. She tends to listen to ambient noise playlists (rain, etc.)
Has anyone tried the tracks from Music To Code By (http://mtcb.pwop.com/) ?
I bought a few of them and IMO they are nice. The tracks are all 25 minutes in length.