Go on 8tracks and search study for some good playlists. Classical would be good so composers such as:
-Hans Zimmer (Interstellar Main Theme)
-Yiruma (River flows in you)
Or maybe for a relaxing (but not necessarily classical) instrumental, choose songs from Studio Ghibli such as:
- Itsumo Nando Demo
-Inochi no Namae (one of my faves)
Or some bossa nova tracks such as:
- Make it Mutual by Olivia Ong
- More than Paradise by port of Notes
Or some relaxing electronic music such as:
-Sunset lover by PETITE BISCUIT