Question: What was an unreleased song created by a female artist who left a band and started a solo career in 2004?
Sentence (from "Gwen Stefani"): She is a co-founder and the lead vocalist of the band No Doubt that experienced major success after their breakthrough studio album "Tragic Kingdom" (1995) along with various successful singles, including "Just a Girl", "Don't Speak", "Hey Baby", and "It's My Life".
Relevant evidence: Yes