In 1943, the electronic music pioneer Daphne Oram, who has died aged 77, began work as a music balancer for the BBC in London. Within five years, she was making her own experiments with synthetically created sound.

Among her early instrumental compositions, the unperformed, 30-minute Still Point (1950) stands out. In it, the orchestra is combined with prerecorded instrumental sounds and live treatments - using standard radio equipment of the period. It is almost certainly the earliest composition to specify the real-time electronic transformation of instrumental sounds.

By 1956, Oram's attempts to convince the BBC of the value of electronic music and musique concrete were bearing fruit. She assembled a temporary, late-night studio - which operated after broadcasting had finished - to produce background music. Two years later, she was appointed the first director of the BBC's new radiophonic workshop, but by January 1959, unhappy with the music department's lack of interest, she went freelance, moving to Tower Folly, a converted oast-house, near Wrotham, Kent, with her studio located in a circular room at the base of the tower.

To earn a living, she created electronic music for theatre, radio, television and industrial and publicity films - her sinister electronic underlays featured in the 1961 Deborah Kerr film, The Innocents. She composed music for two ballets and several concert works, including Four Aspects (1960). She released Electronic Sound Patterns, from the LP series Listen, Move And Dance, and provided the melody for the Nestea television advertisement. In 1968-70, she produced tape parts for three compositions by Thea Musgrave, two for a solo instrument and tape, and the ballet Beauty And The Beast.

Oram was born in Devizes, Wiltshire. She studied at Sherborne school for girls, and had private lessons for piano, organ and composition.

Her dream was to create a machine with which the composer could "convert graphic information into sound", bypassing the more laborious methods of cutting and splicing tapes used in electronic music studios. This became a reality in the 1960s, with Gulbenkian Foundation funding, after which she reduced her commercial work, although in 1982-89 she gave electronic music classes at Christ Church College, Canterbury.

The Oramics system (1962-65) was probably the most sophisticated of several graphically-based composition machines that were constructed between the 1930s and 1960s. In the 1980s, new digital techniques made it increasingly obsolete; it is in a private collection in Devon, in need of restoration. Funded by the RVW Trust and the Arts Council, from the mid-1980s Oram began working on a digital version with an Archimedes RISC computer.

My first contact with Oram was in 1961, while I was a music student, when she generously invited me and a friend to stay for a weekend; it was my first experience of working in an electronic music studio.

She never lost her love for the classical music repertoire; Schubert's string quintet was her favourite piece of music. In the late 1980s, she initiated Out And Round About With Music (Oram), playing music in the open-air to less mobile older people. During the 1980s and early 1990s, she was active in the Performing Rights Society, introducing the provision of Christmas hampers.

Oram's death follows that of the other woman pioneer in the medium, Delia Derbyshire (obituary, July 7 2001). But unlike Derbyshire, who was able to work in electronic music studios, Oram came from the generation that had founded the studios, despite resistance and indifference. Her independent outlook is illustrated in her idiosyncratic, almost mystical, book An Individual Note Of Music, Sound And Electronics (1972).

Oram never married; she is survived by her two brothers.

· Daphne Blake Oram, composer and inventor, born December 31 1925; died January 5 2003