This Max for Live device allows your MIDI sustain pedal work in 3 different ways, like a sostenuto pedal, like a freeze pedal, or like a combination of the two.
Sostenuto Mode: Works like a normal sostenuto pedal (the middle pedal of a grand piano). The moment you press the pedal, all currently held notes will be sustained until the pedal is let go. All notes played after the initial pressing of the pedal will release normally.
Freeze Mode: Overlapping notes held or played after the depression of the pedal will be held till the pedal is let go, or a new set of overlapping notes is played, which clears the previously held notes and replaces them.
Sostenuto Freeze Mode: A combination of sostenuto and freeze mode. Once the first set of overlapping notes is played during or after the pressing of the pedal, all other notes will release normally.
There's also a fold out out keyboard display to help you see which notes are being held.
Demo Video: https://youtu.be/oS7TWDb2xSs
Special thanks to B for the idea for the device! Send any ideas you have to firstname.lastname@example.org.