Step 7: Final assembly
Insert one street sweeper bristle and tune it roughly to a C note. Mark it and "cut" it to length, actually I just put it in a vice and broke it. File and sand it carefully to round and smooth the ends, if you don't it will make a sound scraping across your finger prints or worse scraping off your finger prints! Re-insert it under the "clamp" and do the same for each of the notes you want, I added a total of 9. If you want more you'll have to either make the whole thing bigger or space the keys closer than I'm comfortable with. I put in keys for C through G then A through D in this pattern:
The pattern was suggested by a friend that had a bit more experience with musical instruments than I have, but other people have since made other suggestions so arrange them in any order you're comfortable with.
When they're all in, tune them carefully and tighten down the screws until you don't hear any buzzing when you play it.