Career
He is currently the guitarist of German metal band Kreator. He spent part of his life in Germany and thus has strong ties with the German metal scene. German "Rock Hard" magazine featured him in 2007 as "forgotten guitar hero".
While living in Germany, he served as a session musician for rock band In Rags, gothic act Tiamat and thrash metal band Grip Incorporated.
Foreign both Tiamat and Grip Incorporated., he played sitar, his second favourite instrument. Waltari (1989-1995, 2001-present)
Yli-Sirniö originally joined experimental Finnish crossover legend Waltari in 1989, left the band 1995 to live in Germany and returned 2001.
So far he recorded 8 studio albums with Waltari. Yli-Sirniö likes to explore other opportunities and has many guest appearances with other bands.
Kreator (2001-present)
He also replaced injured Swiss guitarist Tommy Vetterli (of Coroner fame) on some live dates for Teutonic thrash metal pioneers Kreator.
In 2001, Vetterli departed and Sirniö was asked to replace him on a permanent basis. He also appears on the Live Kreation double-album and Digital Video Disc, released in 2003.