Ognian Vassilev is a graduate of the National Academy of Music with a Diploma in Choral Conducting from 1977. In addition, he has specialized in chamber music in Bayreuth, Germany, and in choral conducting technique in Albena, Bulgaria. He has worked as the artistic choir director for the Bulgarian Television and as a teacher of choral conducting at the Academy of Music, Dance and Fine Arts in Plovdiv. With his Bulgarian choirs, he has won several awards at choir competitions in Bulgaria, Ireland, Germany, Italy, and France.

Ognian Vassilev has moved to Finland in 1991. There, he has founded the Pori Philharmonic Choir in 1995 and has served as its conductor, as well as the conductor of the Pori Opera Choir, from 1995 to 2020. In 1997, he has founded the mixed choir Tempori and the chamber choir Sempre. With his choirs from Pori, he has successfully participated in numerous international choir competitions in Spain, Germany, Malta, Venice, and Prague 2012.

He has also served as the choir director of the cultural department in the city of Pori from 1997 to 2020. The Finnish Choir Association has elected him as Choir Conductor of the Year in 2011. In 2020, he was awarded the Order of the White Rose of Finland – First Class Medal with Golden Cross.