I'm an enormous fan of Cobain & Nirvana. There's a demo recording of Kurt covering And I Love Her, which is really cool. Butch Vig, the producer of Nevermind, has mentioned numerous times over the years that Kurt hated double-tracking his vocals as needed. So, whenever Cobain would protest against doing so, Butch would remind Kurt, "Lennon did it!" and Cobain would always relent. haha.