I love that the "notation" looks like line noise. Well, it would if it had more tildes anyway. ;)

A cheap MIDI controller is, well, cheap, and most are at least velocity sensitive. A pressure sensitive one is a good bit pricer, but that's not as important. You can also find cheap, used older synths with half-keyboards that make fine controllers too. I had a Juno 1 I often used as a controller but there are many others you could use.