Short answers, pulled from the story.
The Roland TR-808 drum machine was released in 1980 and only about 12,000 units were built before production ceased. This device became a commercial failure initially but later became the most influential invention in the history of popular music.
Léon Theremin invented the Rhythmicon drum machine in 1930 at the request of composer Henry Cowell. This early device used vacuum tubes and rotating mechanical discs to produce sixteen different rhythms tied to specific pitches.
The Linn LM-1 Drum Computer was the first drum machine to use digital samples of real drum kits and it launched in 1980. This machine was priced at $4,995 and only about 500 units were ever made.
The Roland TR-909 drum machine was released in 1983 and it had a lasting influence on techno and house music. This machine was the first Roland drum machine to use MIDI and samples for some sounds.
The Roland TR-808 drum machine uses a 16-step bar to create rhythm patterns where individual sounds are placed at specific points. This programming method allows musicians to build complex percussion tracks from scratch.