If you are new to MIDI or want to go over some basics, this is the best place to start.
Here is where you'll find guides to understanding what MIDI is, what it's not and general information everyone who uses MIDI should know.
There are Categories for MIDI 1.0, MIDI 2.0 and MIDI History.
The golden age of mechanical music machines really came in the late 19th century and early 20th century with player pianos and orchestrions. A player piano is defined as any actual acoustic piano that is played by a pneumatic or electro-mechanical mechanism that operates the piano action via pre-programmed music.