Question: How many episodes are in the 2014 American documentary about a band who's frontman is Dave Grohl?
Related documents: [0]  [DOC] Sonic Highways is a 2014 American documentary miniseries directed by Dave Grohl and written by Mark Monroe. The documentary was made concurrently with Foo Fighters' eighth album, "Sonic Highways", and was broadcast on HBO. Grohl described the project as "a love letter to the history of American music". Each of the eight episodes is presented as an exploration of the musical history of a different American city through a series of interviews by Grohl. The group is also shown incorporating what they learned from the interviews into the writing and recording of a new song in or near that city. The series debuted on October 17, 2014. [END] 
[1]  [DOC] David Eric Grohl (born January 14, 1969) is an American rock musician, guitarist, singer, drummer, songwriter, record producer, and film director. He is the former drummer of the grunge band Nirvana and the frontman and founder of the rock band Foo Fighters, of which he is the lead vocalist, rhythm and lead guitarist, and primary songwriter. [END] 
Answer: 
eight
eight