StringSeq
Karplus-Strong Synthesis and a Sequencer
read Digital Synthesis of Plucked-String and Drum Timbres for more info
I didn't, this is taken from some Github repo and beaten into submission
(and added some additional features)
Javascript made this sequencer really easy
I don't know how to center a div
Click or Hold the left mouse button to place notes
Click or Hold the right mouse button to remove notes