Bjørn G. Gjerstrøm was born in Oslo in 1939. His earliest musical influences he received at home from his parents, composer Gunnar Gjerstrøm and music teacher Elsa Gjerstrøm. He started learning the piano from his mother at the age of four and completed his first composition only nine years old. Norsk Notestik & Forlag were responsible for Gjerstrøm's first published work, five pieces for the piano, which the composer himself performed on Norwegian and Swedish radio at the age of twelve.
Trygve Lindeman and Conrad Baden were his teachers at the music conservatory in Oslo in the 1960's, where he studied music theory, harmony and composition as well as continuing studying the piano with Waldemar Alme and Ivar Johnsen. From 1969-76 he was a composition student of Hallvard Johnsen.
Gjerstrøm's extensive list of works includes music for film, orchestra and various instrumental groups; he has written solo pieces for piano, flute, oboe, guitar and accordion, and songs to poems by Peter R. Holm, Stein Mehren, Arnulf Øverland and Elsa Gjerstrøm, among others.
One of his most important earlier works is the Concerto for Piano and Orchestra op. 7, first performed in 1983 by pianist Kjell Bækkelund and the Oslo Philharmonic Orchestra under Per Dreier. This works has since been performed in Stavanger and Bergen, and the following excerpt of a review by Roland Lengauer was to be read in 1984: "The composer's musical language is not modern in the true sense of the word; this should never be used as a criterion for the assessment of music from our own time. For Gjerstrøm's music does belong to this age, and not least - perhaps in fact the most important criterion for this reviewer - it displays a considerable talent for composition; Gjerstrøm's music is full of ideas which he has the ability to develop further. The piano part is proof of the composer's knowledge of the possibilities this instrument has to offer."
Ved havet (By the Sea) op. 5, released in 1996 on the CD 20th Century Bækkelund, is the most often performed of Gjerstrøm's piano works. Morten E. Pedersen wrote the following excerpt of a review for the magazine Nye Musikken: "This piece successfully balance compositional technique and the composer's delight in the musical narrative, contained within a musical language of moderate tone-colour". Pianist Øyvind Aase performed the Piano Sonata op. 28 during the Grieg Anniversary in 1993, prompting Arvid Vollsnes to comment in Aftenposten: "A fine, pianistic work with rhythmic drive and exciting sounds."
Music critic Jarle Søraa wrote in his review of the CD Two Composers - Two Generations, selected chamber music of Gunnar & Bjørn Gjerstrøm (1996): "Both Gunnar Gjerstrøm and his son Bjørn G. Gjerstrøm are full-blooded romantics. Gjerstrøm jr. is, as his father, highly inspired by nature; one can hear this is the alternately wide, undulating and dusky, nocturnal piano pieces Camara de Lobos op. 8.
And the following was expressed by the composer himself when interviewed about his music: "I grew up with a father who composed music in a late Romantic, impressionistic idiom; it was only natural that this music tradition influenced my earliest compositions. Later works are more stylistically varied; studies with Conrad Baden and Hallvard Johnsen brought me into contact with freetonal and 12-note composition, which has influenced my music in the direction of a generally freer tonality. In my most recent works I have employed a more texturally orientated expression, in keeping with a more modernistic style."
Gjerstrøm is a member of NOPA - Society of Composers and Lyricists and the Society of Norwegian Composers.