Formed by Tool vocalist Maynard James Keenan and former Tool guitar tech Billy Howerdel, A Perfect Circle is an extension of the alt-metal-fused-with-art rock style popularized by Tool in the early to mid-'90s. While similar to Tool in intensity and melancholy, A Perfect Circle is less dark and more melodic, with a theatrical, ambient quality that incorporates occasional strings and unusual instrumentation.
A Perfect Circle released their debut album, Mer de Noms, in 2000. Thirteenth Step followed in 2003, and the covers album Emotive appeared in 2004.