SL THEORY were created by Sotiris Lagonikas back in 2009 as a one-man band, releasing three albums, “I”, “Progressively Dark” and “Different Space, Different Time” until 2017, when SL THEORY became a full member band with the addition of Manos Gavalas (keys), Alex Flouros / Giannis Nigdelis (guitars), Chris Kollias (bass), Mike Karasoulis (lead vocals) and Margarita Papadimitriou / Christina Alexiou / Kandia Bouzioti / Alexandros Louziotis (backing vocals) and released the live CD/DVD “Progressively Dark – A Concert For Group & String Orchestra” from the band’s superb concert at “Passport Live” on March 2017, where SL THEORY along with presented live their “Progressively Dark” album along with a string orchestra conducted by Maestro Yiannis Antonopoulos. As of the beginning of 2019, the backing vocals are handled by Sotiris Lagonikas / Manos Gavalas / Giannis Nigdelis along with expert vocalists Margarita Papadimitriou and Anna Tarba and “CIPHER” is the first studio album that the band recorded with this line up.