Along with her contributions with the band, Lee has also participated on numerous other musical projects including Walt Disney Records' Nightmare Revisited and Muppets: The Green Album.
Lee has performed collaborations with artists such as Korn, Seether, and David Hodges.
She performed backup vocals for "Missing You", a song on Big Dismal's 2003 debut album Believe, and sang backup vocals on two songs with 'supergroup' The Damning Well, though her vocals were taken off the final release due to record label issues.
Lee later performed a duet with her then-boyfriend Shaun Morgan on the track "Broken" for Seether's 2004 album Disclaimer II.
In 2000, Evanescence recorded the longer EP Origin.