Ardour's handling of MIDI editing differs from most other DAWs and MIDI sequencers.

Key features of Ardour MIDI handling

• All editing is done in-place, in-window. There is no separate piano roll window or pane. Edit notes right where they appear.
• MIDI, just like audio, exists in regions. MIDI regions behave like audio regions: they can be moved, trimmed, copied (cloned), or deleted. Ardour allows either editing MIDI (or audio) regions, or MIDI region content (the notes), but never both at the same time. The e key (by default) toggles between region level and note level editing
• Editing note information in Ardour occurs in only a single region. There is no way currently to edit in note data for multiple regions at the same time, so for example notes cannot be selected in several regions and then all deleted, nor can they be copied-and-pasted from one region to another. Region(s), though, can be copy-pasted just as with audio.
• When using jackd as the audio server for Ardour, all MIDI I/O is done via JACK for sample accurate timing and maximal efficiency when communicating with external software synthesizers. Otherwise, Ardour connects to midi via the existing OS MIDI system.
• Every MIDI track has its own MIDI port for input; it may have an arbitrary combination of audio and MIDI outputs, depending on the signal processing in the track.
• Full automation for MIDI tracks, integrated with the handling of all MIDI CC data for each track.
• Controllers (CC data) can be set to discrete or continuous modes (the latter will interpolate between control points and send additional data).
• There is a Normal and a Percussive mode for note data editing.
• The scroomer is a combination scroll/zoom tool for altering the zoom level and range of visible MIDI data.

Notable Differences

• Fader (volume) control currently operates on transmitted MIDI data, not by sending CC #7.
• All note/data editing is per-region. There are no cross-region operations at this time.
• By default, copying a MIDI region creates a deep link—both regions share the same data source, and edits to the contents of one will affect the other. Breaking this link is done by selecting MIDI > Unlink from other copies from the region context menu, after which the selected region(s) will have their own copies of only the data that they visually display on screen. The region will no longer be trimmable back to its original length after an Unlink operation, and the operation cannot be undone.