Each of these bands was in crisis in the mid-to-late 1970s: Led Zeppelin were plagued by discord and personal tragedies and had drastically reduced their activities, Black Sabbath finally fired their charismatic but unreliable frontman Ozzy Osbourne, and Deep Purple disbanded.
Cada un destes grupos sufriron crises a mediados e finais dos anos 1970: Led Zeppelin viuse envolto en discordias e traxedias persoais que reduciron de forma drástica a súa actividade, Black Sabbath despediu o seu carismático pero pouco fiable vocalista Ozzy Osbourne, e Deep Purple separouse.