Classical, OST, or anything without words or in a language I don't speak. If I listen to anything else I'll probably get too involved with the words and slow down writing or stop all together.

Just some of the stuff I might put while writing.
[url=https://www.youtube.com/watch?v=tFIbVqHOOIU&list=FL0yJYqThLk-X-bv6JMtsi2Q&index=23]Witcher OST[/url]
[url=https://www.youtube.com/watch?v=npsAcevrIzk&list=FL0yJYqThLk-X-bv6JMtsi2Q&index=24]Witcher 2 OST[/url]
[url=http://youtu.be/vn_whTR8gy4]Witcher 3 OST[/url]
[url=https://www.youtube.com/watch?v=OO7kW_-u2y0]Uncharted 3 OST[/url]
[url=http://youtu.be/qNAp0igLZIs]Allen Toussaint's The Bright Mississippi[/url]
[url=https://www.youtube.com/watch?v=CY298YD2kZw]Misc. collection of Russian Waltzes[/url]
[url=http://youtu.be/GRxofEmo3HA]Vivaldi[/url]

[url=https://www.youtube.com/playlist?list=PLOZr_k-1GdZ8kfGqI-3lmFUeyBs7h2Y2H]And then I got this.[/url]