This patch allows using sostenuto pedal (or signal) on any instruments that may not support it natively (it will sustain notes that were held when pedal was pressed, but not affect new notes after it, and will release sustain as pedal releases).
If your sostenuto pedal uses specific CC message, set it accordingly in top-left corner of the patch.
Check the notes in the patch on how it works.
After much discussion I've finally figured out that this patch I've made is for Sostenuto effect specifically, and not usual Sustain pedal action. by x.iso