In 1975 Spasov graduated in composition from the Moscow Conservatory, then became a research associate at the Musicology Institute of the Bulgarian Academy of Sciences. He is familiar with contemporary developments, including those of Stockhausen and Berio, and is representative of the generation of young Bulgarian composers of the 1970's and 80's in that he distances himself from his material to achieve musical clarity. His orientation is to the deeper levels of consciousness, specifically to medieval texts, whose complex semanticism he has sought to codify with a variety of effects and contrasts in instrumental and vocal music.
In Glagolicheskiyat kontsert (Glagolitic Concerto), based on 13th-century sources, the solo female voice is intertwined in the multi-layered texture as an additional timbre, using the text as musical sound material.
The chamber opera-ballet Omagyosaniyat (The Bewitched) is a parable about love, jealousy and unfaithfulness, and freedom and its denial. Dramatically it is close to Stravinsky, and the work may be seen as a mosaic of various compositional styles.