You were doing me a favor, Kevin, since I play along a lot with favorite recordings and with band-in-a-box. In fact, I was so impressed with the new sound of my Suzuki M-32C that I spent several hours today re-tuning my favorite P-32D Pianica to A440. Also, sometimes I have the opportunity to play along with a piano.
I’ve seen that video and others by that guy. He’s quite a character. I would be worried about sand from the sandpaper getting into my melodica, and his arrangement for it seems awkward. I’m abrading and scratching more than scraping, lightly of course. It’s just a matter of lightly removing some material. I noticed that some of the factory tuning is in the form of random scratches that look like they have been done with a sharply pointed tool of some kind.
I don’t put the whole melodica back together, but I do tightly screw down the reed chamber cover, which I had to do and undo about 8 times today with my pianica. I start by getting readings for all the notes, going through that process several times until I’m satisfied that my final readings are in the right vicinity, with special attention to any extreme readings and to wide divergences. I then focus on just the notes that are more than 3 cents off the standard. Then I open the melodica up and scrape all the reeds, guestimating how much to scratch/scrape them in relation to how far off they were. Then I screw the cover back on and go through the “readings” process. Then focusing again just on the notes that are still 3 cents +/- off, I remove the cover and do more scraping in proportion to how far off the remaining reeds are. I repeat this whole thing as many times as is necessary, sometimes doing a tiny bit more scratching on reeds that are almost 3 cents off.
My guess is that factory tuners just take note of reeds that are not within some margin, go in and do some scraping, and call it good. Obviously some of them would get better results than others.
The whole process is laborious and can get very frustrating, so I need to take some breaks and go do something else. But it’s a kind of thing I enjoy doing and find satisfying.
I’ve heard that some people use a dremel. I got one for Christmas, but when I showed my daughter who makes jewelry the reed plates of a melodica, she advised me against using it for that purpose.