"A Sphere In The Heart Of Silence" is the fifth album in a series of six solo efforts that John Frusciante undertook from June 2004 to February 2005.

It is an album of mostly electronica based material, and was a joint collaboration between John Frusciante and Josh Klinghoffer, who following Frusciante and joined the RHCP as guitarist in 2010, staying until 2019.

Both of them perform vocals; John Frusciante sings lead vocals on "Afterglow", "Walls" and "My Life", and shares vocals with Josh Klinghoffer on "Surrogate People".

Josh Klinghoffer performs lead vocals on "Communique", "At Your Enemies" and does the backing vocals for "Walls".

John Frusciante calls Sphere in the Heart of Silence "a record of electronic music," but it's not nearly as "electronic" as that statement makes it sound.

It's really more an allusion to the fact that his other releases of this year have been mostly comprised of guitar, bass and drums, and that there is some programming, synth-work and overdubbing on this one.