RtMidiInMessage

Table structure containing a realtime MIDI input message.

number timestamp
The number of seconds that have passed since the last message was received.
This will be 0 for the very first message received, or when calling RtMidiIn:GetMessage when there are no messages in the queue.

table message
The message, as a table of bytes.
This will be empty when calling RtMidiIn:GetMessage when there are no messages in the queue.
The first byte represents the message status, potentially followed by data bytes.
What each data byte represents will depend on what the status byte is.
See the MIDI 1.0 specification for more information.