Sotiris Lagonikas (born 17 June 1970) is a Greek musician, best known for his work as co-founder and drummer of the Greek classic rock group What's The Buzz?, as well as for his SL Theory music project,
where he has composed the music and written the lyrics while performing all instruments and vocals
recorded on his debut album which was released in 2010 under the title "SL Theory - I".
Two years later Lagonikas released his second solo album, under the title "Progressively Dark" and by the spring of 2013,
along with longtime friend and What's The Buzz? co-founder Chris Kissadjekian under the band name Double Treat, their debut album "Wander Thirst" was released though Sleaszy Rider label.
The second album of SL Theory was released December 2014, under the title "Different Space Different Time" followed by 2018's live album "Progressively Dark - A Concert For Group and String Orchestra" which was released through Melodic Revolution Records in double-CD and DVD formats.