does it simply extend the midi notes?

or does it do something else?

 

Something else it's called a sustain pedal. They are on a piano to give the notes resonance. Sort of like reverb.

 

You hold the notes with the foot and don't need to hold them with your fingers down any longer.
On a real piano this has an additional effect because all the strings a swinging freely and even the ones you don't play are stimulated to vibrate/resonate.

 

As long CC64 is active (127), MIDI Note Off message is ignored until is 0 again.
MIDI roll notes are not touched , but only sound sustain due to the missing Note Off MIDI message.
From your roll example, you could try to shorten notes, but as long they are triggered once and within the CC64 ON (127), they will sound sustained until the next chord.
Hope it helps.

 

@No Avenger explained what happens with the Sustain pedal on a piano. There's also a Sostenuto pedal that's similar but it only holds notes that were On when the pedal was pressed. People use it to hold chords and play melodies over the held chord.

@orbitbooster explained how midi is supposed to emulate the behaviour of those pedals.

In practice... 'You hope' that your DAW handles MIDI CC 64 Damper/Sustain and MIDI CC 66 Sostenuto
in a way that emulates you using the pedal on a real piano.

That means (roughly) that even though a recorded midi note is supposed to issue a 'note-off' event, if there was a pedal event CC 64 current at that time then the note-off will get ignored and the note will sustain until the CC 64 ends.
That means the recorded midi note does not (should not) need to be lengthened (in the editor) in order to play the sustained length.

But if you actually 'wanted to' lengthen the midi notes (in the editor) and then do away with the CC 64 events it would be down to how much help can your DAW provide. In Logic (for example), there is a function called "Sustain Pedals to Note Length". It analyses the sustain pedal events (CC 64) on selected notes, and (destructively) lengthens the recorded midi notes, so that they sustain until the CC 64 off message is reached. And then it erases the redundant pedal events.
Maybe other DAWs provide something similar.

 

Hit the key and immediately after push the pedal.
It works pretty (very) well in the NI series pianos, basically it sustains the tail of the note, just after the peak, it gives a touch of realistic behaviour.

I don't have a continuous pedal controller, but with real pianos, unless well maintained and possibly high end, it doesn't work very well (stiff pedal, unbalanced dampers rail, etc).
As far as I know it's not a very used technique in anyway, but I'll investigate on it.

 

Last edited: Apr 3, 2021