Step 1: Materials:
For most of the parts I was looking for stuff I had sitting around. This is the parts list for what I ended up with.
(2) - 3/16" plywood - 5" x 7" for the top and bottom
(2) - 3/4" x 3/4" x 3' pine - 5" and (2) 7" for the frame
(2) - 1/4" dowel - 2-1/2" to support the keys
(1) - 3/8" aluminum rod - 4" to hold down the keys
(1) - 3 1/2" nail - cut to 3-1/4"
5/8" x 18 brads - optional
(2) - #6-32 x 1/4" T-nuts
(2) - #6-32 x 1" round head bolts
street sweeper bristles - enough to make 9 keys about 2-1/2" - 3-1/4" each.
I had to buy the T-nuts and bolts but the rest I was able to scrounge. The "keys" were made out of street sweeper bristles. They're easy to find if you get out and walk much, just keep an eye on the street.
Step 2: Cut out the wood parts
Step 3: Front face
I drilled the 1" hole part way through the back then turned it over and drilled the rest of the way from the front to avoid splitting either side of the plywood.
When I was done I found that 4-1/2" seems a bit too close to the T-nuts you could move it a half to an inch further down. Also I found out that a 1" hole seems to make the higher notes sound louder, epically the B key. A smaller hole would tend to shift the emphasis to the lower notes. Using a 1/2" drill gauge held over the 1" hole seemed to bring out the F note.
Drill the 3 holes and tap the T-nuts into place with a hammer.
Step 4: Assemble the box
- set it aside to dry
Step 5: Dowels and Rods
Cut the head and point off of the nail (3-1/4") and file the ends flat. Put it in the drill press to round the ends and clean as with the aluminum rod.Cut 2 lengths of the 1/4" dowel to 3-1/4". Flatten both dowels along the length just enough so they don't roll easily. Hollow out a channel on the side opposite the flat of one of the dowels to "cradle" the nail in place. I did this using a motor-tool while holding the dowel in a vice.
Set these parts aside for now.
Step 6: Sanding and finishing
Dust it off carefully and put a coat of varnish on it. I put the bolts in the T-nuts so I could hang the box up to dry without it touching anything. When the varnish is completely dry rub it down with fine sand paper or steel wool to get a nice smooth finish. Put as many coats of varnish as you like.
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.