He joined the engineering department of Western Electric in 1917, and became an employee of Bell Laboratories in 1925.
[4] Keller's invention of a "moving-coil" playback stylus made possible the first hi-fi records.
In 1931-32 Keller made the first known stereophonic and high-fidelity recordings of orchestral music.
Keller led the design team at Bell Laboratories which developed the first modern wire wrap tools.
Keller was awarded the Gold Medal from the Audio Engineering Society in 1981 for outstanding developments in stereophonic disk recording.