He was born in Finland on 14/10/1929. He studied singing in Helsinki (1957-1959), Stockholm with Martin Φhman (1959-1960) and finally in Rome with Luigi Ricci (1963-65). His made his debut in 1961 at the Helsinki National Opera as Radames in Aida, and continued performing there until 1965. He subsequently collaborated with the Deutsche Oper am Rhein Dusseldorf Duisburg until 1967 appearing mostly in Italian repertoire, such as Radames [Aida] and Chenier [Andrea Chenier]. In the years 1965-1976 he sang in Staatsoper Stuttgart. Mustakallio performed in major opera houses in Scandinavia and Germany, mostly in Helsinki National Opera, Munich State Opera, the Opera House at Nόrnberg, and at the Opera Festival in Savonlinna (Finland), where he was hired as artistic director in 1980. He also sang masterfully lieder cycles by Brahms, Beethoven, Schubert and Sibelius. In Germany and Italy he became known as Timo Callio. Mustakallio sponsored an annual vocal competition bearing his name. He recorded with Finnish labels and died in Helsinki (Finland) on November 1984. He appeared at the National Greek Opera as Calaf in Turandot during the 1968-69 season.