The early music ensemble and orchestra Opus X was founded in 1995 at the initiative of violinist Petri Tapio Mattson, who is also the ensemble's artistic director. The members have studied with leading early music specialists like Jaap Schröder, Wouter Möller, Lucy van Dael, Marcel Ponseele and Bob van Asperen, and have also played with renowned orchestras such as the Orchestra of the 18th Century and the Freiburg Baroque Orchestra. They have performed a wide variety of chamber repertoire ranging from Italian Early Baroque to quartets by Haydn, Mozart and Crusell. The ensemble has performed large-scale choral and orchestral works, such as Bach's St John Passion, St Matthew Passion and Mass in B minor, Mozart's Requiem and Handel's Messiah and Water Music. With the two concerts at the Schleswig-Holstein Musik Festival in 2001, Opus X was the first Finnish Baroque orchestra to appear at an international music festival outside Finland.
Since 2004 the ensemble has collaborated with the renowned early keyboard instrument specialist Miklós Spányi in recording the keyboard concertos and sonatinas by C.P.E. Bach for BIS Records. In 2005 Petri Tapio Mattson stepped down as the artistic director and was replaced by Miklós Spányi.
