The first is the pianorad the second is the staccatone

In 1923 Hugo Gernsback introduced the Staccatone, which was sort of a synthesizer that capitalized on the technology from the vacuum tube, and used oscillators to produce musical notes. Every note required its own oscillator and had a tendency to fade in and out of tune.

In 1926 he came out with an improved version of the Staccatone, which he renamed the Pianorad. It had twenty five oscillators and could cover two octaves. Each oscillator was connected to its own speaker, all of which were connected to a loudspeaker horn to provide amplification and was the first polyphonic keyboard. From the inside, it looked like a cabinet filled with lightbulbs and other tubes. Grensback had this to say about his invention in his own magazine:

The musical notes produced by the vacuum tubes in this manner have practically no overtones. For this reason the music produced on the Pianorad is of an exquisite pureness of tone not realised in any other musical instrument. The quality is better than that of a flute and much purer. the sound however does not resemble that of any known musical instrument. The notes are quite sharp and distinct, and the Pianorad can be readily distinguished by its music from any other musical instrument in existence.”

In other words, he had created the first sine wave oscillator, as well as the first keyboard where it was possible to play more than one note at a time.

Although the pianorad never cough on with the mainstream public, Gernsback did play the Pianorad on his radio station in accompaniment of pianos and violins