According to Vig, Cobain's impatience with recording multiple vocal takes made it difficult to acquire a master vocal take. In the 2005 documentary "", Vig revealed the methods he used to get Cobain to record multiple takes, which included tricking him into believing that certain parts were not properly recorded and needed to be done again, and reminding him that the Beatles' John Lennon double-tracked his vocals in the studio. The varying intensity of Cobain's vocals from one take to the next, and from the verses to the choruses, also presented a problem for Vig, who had to adjust the input levels "on the fly" while recording Cobain. Ultimately, Vig was able to edit several takes together into a single master, due to the consistency of Cobain's vocal phrasing.