[PD] How to add/remove MIDI notes from a list using MIDI in and note on/off?

[JC Pedroza]

I need to populate a list with the MIDI notes that are being pressed, and remove the note from the list when the key is released. 

One idea is to use [notein], and if the velocity is> 0 then add the note to the list, and if the velocity == 0 then remove the note from the list. But I have no idea of how to implement this.

I think I need [list-extend], [list-find], and [list-delete], but I just can't figure out an implementation. 

How can I do this?