Even if you don’t like Steely Dan, this 1999 documentary about the making of their 1977 album Aja is fantastic. (The first segment of the YouTube vid might be blocked in your country; watch via this link if so).
First off, the Aja documentary is fucking hilarious—Walter Becker and Donald Fagen come across as the smartest, most venomous guys in the room—a wicked mixture of witty and cruel—-and watching them discuss each track, and each part of each track is fascinating (especially when they pick apart failed guitar solos). The film also features a marvelous supporting cast, including braggart percussionist Bernard Purdie (of “The Purdie Shuffle” fame), and poor old Michael McDonald, who struggled to nail his background parts on “Peg.” What might be most fascinating though is seeing how Fagen and Becker pieced the instrumental tracks of Aja together, bringing in different session musicians—entirely different bands—from day to day. And if you’re still not convinced, here’s a sample (of a sample):