In 2001 former Nirvana drummer and current Foo Fighters front man Dave Grohl had penned two songs called "Sweet Dreams" and "My Tortured Soul" for the new Ozzy Osbourne album but they were both rejected. This became the birth of the Probot project with which Grohl wanted to pay tribute to the elite of 80s metal. The album was to feature a row of vocalists from the bands Grohl had grown up with such as King Diamond, Celtic Frost frontman Thomas G. Fischer and Cathedral's Lee Dorrian with each singer guesting on a specific song. Unleashed frontman Johnny Hedlund was excluded due to "questionable politics". The album sold 27,000 copies in its first week of US sales and landed at #68 on the Billboard chart.