The MIDI Tracer is similar to the MIDI List Editor, in the way that it displays MIDI information as a tabular text view, and has a vertical flow, i.e. the events follow a top to bottom time order.

Its use is different though, as it is not bound to a specific region or track: the MIDI that is monitored is any global input or output Ardour presents to the system. It is hence a very useful option to monitor a MIDI port, be it an external controller/device or the in/output of any track.

It is accessed by selecting the Window > MIDI Tracer menu.

The window is made of:

Port

a list of all the MIDI ports Ardour presents to the system. They are both internal and external and are the same ports Ardour presents to JACK, if enabled.

the events list

where all the events for this port are listed, see below

Line history

how many lines should be kept in the events list

Delta times

if checked, shows the times as the duration since the last event, instead of the absolute time

Decimal

if checked, shows the MIDI data as decimal values instead of the original hexadecimal values

Enabled

if checked, the events are displayed in the events list, otherwise stops the logging

Auto-Scroll

if checked, the events list scrolls as new events are logged, allowing to keep the newest events on screen

The events list displays the events as columns:

time of the event

either absolute or relative, based on the Delta times checkbox

MIDI status (event type)

what midi events happened (e.g. Note On, Note Off, Pitch Bend, …)

MIDI channel

in which MIDI channel did the event happen

MIDI data bytes (event parameters)

parameters of the event, e.g. for a Note On: what note was it, and which was the note's velocity

Note: The MIDI Tracer can lists all kind of MIDI events, "audio" ones, but also scene automation or timecodes ones.