In 1984, at age 11, Gildenlow formed a band called Reality,[2] which changed its name to Pain of Salvation in 1991,[2] and released its first album, Entropia, in 1997.

In 2001, he joined progressive rock supergroup Transatlantic on their European tour,[3] playing keyboards, guitar and singing.

He departed The Flower Kings due to his opposition to US-VISIT which required submitting biometric data first before entering the U.S.[5] In 2007 he provided spoken word to the track "Repentance" on Dream Theater's album Systematic Chaos, alongside many other guests including Corey Taylor, Steve Vai, Joe Satriani, Mikael Åkerfeldt and Jon Anderson.

[9] In late 2017 he joined The Sea Within, a progressive rock supergroup consisting of guitarist Roine Stolt, bassist Jonas Reingold, drummer Marco Minnemann and keyboardist Tom Brislin.

[11] This band released one self titled album in 2018, which featured guests Jon Anderson (Yes), Jordan Rudess (Dream Theater), Casey McPherson (Flying Colors) and Rob Townsend (Steve Hackett).