Lately I've been occupied with listening to and studying the works of Daphne Oram (1925-2003). Oram was a British composer working with self-made synthesizers. She developed her own system based upon hand drawn sound techniques, which she named "Oramics".
"This method of music composition was intended by Oram to allow a composer to be able to draw an "alphabet of symbols" on paper and feed it through a machine that would, in turn, produce the relevant sounds on magnetic tape." (Wikipedia)
She also used musique concrète techniques, for use in its programming. The first drawn sound composition using the Oramics machine, entitled "Contrasts Essonic", was recorded in 1968.
She was founder of the BBC Radiophonic Workshop and the first to compose scores only produced by electronic sources.
Besides having lectures on electronic music and studio techniques, she published in 1971 An Individual Note of Music, Sound and Electronics which investigated electronic music in a philosophical way.You can hear samples of her music here.