I stumbled across an article on Mix today by Sylvia Massy (producer of Undertow) in which she talks about the challenges associated with recording Maynard’s voice on the album.  Well worth reading, especially for tech heads:

Tool’s Undertow album is filled with blood-vessel-popping screams, like on the song “Crawl Away.” I had heard them in rehearsals, I heard them onstage. But in the studio, Maynard’s screams were lackluster, even with the perfect complement of the C 1000. After several attempts at one of those 10-second screams without a good take, and with his voice obviously wearing thin, I finally asked him to go outside and run around the block five times. This would make him furious, but after doing it he nailed those screams. He was pissed and you could hear it in his voice. The lesson here? Sometimes it’s necessary to make the singer as un-comfortable as possible to get the right performance!

The vocal sessions for Undertow were all about making singer Maynard James Keenan comfortable—and uncomfortable—in the studio. He ended up on an AKG C 1000 condenser, not a typical vocal choice.