How to write chords with MIDI?

Question

How do I write a chord, i.e. a NoteOn of seveal notes on each above the other at the same time line?

What should be the message for this chord.

Answer 1

MIDI is a serial interface, so you can't actually send two 'Note On' commands at the same time - you physically send them one after the other, but the latency is low enough that although they start playing sequentially, the ear cannot detect the delay.