An art-rock band with nu-metal and gothic elements, A Perfect Circle is the side project of Tool singer Maynard James Keenan (b. James Herbert Keenan, 17 April 1964, Ravenna, Ohio, USA) and has attracted an audience made up primarily of introspective and intellectual young rock fans. Their songs can be quirky, melancholy and even depressing, but along with Keenan's main band, A Perfect Circle has been met with considerable critical and commercial success. Sometime Tool/Fishbone guitar tech Billy Howerdel (b. 18 May 1970, USA; guitar) is responsible for the songwriting, while Keenan adds his uniquely eccentric lyrics and Paz Lenchantin (b. 12 December 1973, Mar Del Plata, Argentina; bass/violin) her ethereal musicianship to the band's work.

A Perfect Circle was first formed in 1997 after Keenan, embroiled in legal wrangles between Tool and associated organisations, took some time off to recuperate. He found some relief in plunging into the creation of songs based on ideas suggested by his touring associate Howerdel, and an album's worth of material was slowly polished into being over two years, with the help of Lenchantin, Troy van Leeuwen (b. 5 January 1970, USA; guitar) and Josh Freese (b. 25 December 1972, Orlando, Florida, USA; drums). The rumour-mill attached to a band of as much cult popularity as Tool is always active, and when fans received word of a potential spin-off project, anticipation began to grow. A Perfect Circle's debut show took place at Los Angeles' Viper Club in August 1999 and Mer De Noms appeared the following spring. Howerdel, who had previously co-written for Smashing Pumpkins and Nine Inch Nails, had crafted an epic, surreal set of songs and Tool fans adopted A Perfect Circle with relish. The album set a new record for the highest-ever debut entry for a new band, entering the Billboard chart at number 4. Keenan subsequently returned to Tool to record Lateralus, their hit album of 2001, and A Perfect Circle was placed on hold until further notice.