Another notable figure in the world of drawing music is Norman McLaren, who literally painted or drew directly on the soundtrack portion of his animated films. The soundtrack for his film Neighbors [3], which won an academy award in 1952, was produced this way. Theres a short documentary on his process here [4].
On the more avant-garde side, Iannis Xenakis had designed a computer-based system called the UPIC in the late 1970s in which you could directly draw waveforms and then direct their frequencies over time by drawing into a graphics tablet. He used this to compose his piece Mycenae Alpha [5].
This page [6] has a really great run-down of optical synthesis in general, which includes a number of individuals and systems involved in directly drawing sound and music. Some of the visual sound designs used in these systems are quite striking, for instance the variophone [7] or Yankovsky's painted soundtracks [8].
[1] Demo of my research software here: https://www.youtube.com/watch?v=Tdj5e82nPHQ
[2] https://itunes.apple.com/us/app/oramics/id454505541?mt=8
[3] https://www.youtube.com/watch?v=P-o9dYwro_Q
[4] https://www.youtube.com/watch?v=Q0vgZv_JWfM
[5] https://www.youtube.com/watch?v=yztoaNakKok
[6] http://www.umatic.nl/tonewheels_historical.html
[7] http://www.umatic.nl/tonewheels/historical/vario3.jpg
[8] http://www.umatic.nl/tonewheels/historical/painted_soundtrac...