"This huge and unwieldy system was controlled by a punched paper roll, similar to a player piano roll. A keyboard was used to punch the roll (Olson has his finger on it). Each note had to be individually described by a number of parameters (frequency, volume, envelope, etc.) The output was fed to disk recording machines, which stored the results on lacquer-coated disks. One of these can be seen at the left in the above photo."
RCA Synth feature, with mp3 audio samples from four 45 RPM extended-play disks