Ø was a pseudonym used by [a4725] (born 1963, Helsinki, Finland - died 12 April, 2017, France, aged 53) a Finnish electronic musician, composer and producer.

He began his musical career playing electronics and drums as part of the early Finnish industrial and noise scene. In 1993, together with [a11329] and [a549915], he founded the minimal electronic group [a3822]. Sami Salo left Pan Sonic in 1996 and the project continued as a duo until disbanding in 2009. Vainio then established a successful solo career, often collaborating with experimental French composer [a669623].