You just need a small file, like a point file. Any gasheads remember those? And a single edge razor blade or the like to lift the reed.
To raise the pitch, you file the end of the reed, making it lighter so it vibrates faster.
To lower the pitch, you file near the attached end of the reed. I am not sure on the physics of this and would appreciate anyone's insight.
The specific tuning I've done many times is to convert a standard diatonic harp (the Richter tuning) to what is now called the Melody Maker tuning.
The Richter tuning was apparently designed for "campfire songs". You could just "blow, man, blow" and all the chords would sound OK.
Later, blues musicians discovered that you could emphasize the draw notes, the ones that are easy to bend to a flat note to get that bluesy sound. This is called "cross harp". For example, in a song in G you would use a C harp instead of one tuned in G.
The problem with cross harp is that the 7th is a minor 7th and you have no way to raise it up to a major 7th if that would fit your song. And the 2nd is completely missing! In fact you just have the tonic (G in this case) on both the draw and blow notes where you might hope to hit the 2nd (A). There is no A in this scale, only the G twice.
To imagine a song where this may be a problem, think of the first three notes of the Beatles song All My Loving. It starts with 3-2-1. Oops, I ain't got the 2. Just the 1 twice.
This is where the file comes in. You raise the blow 1st to a major 2nd. And you raise the minor 7th to a major 7th in both octaves.
Now you have a harp with that bluesy sound we all love, but in a major scale!
Re: lower pitch, I'd hazard a guess that you're basically reducing the restoring force, so the resonant frequency goes down. Think of the attachment point as a bunch of springs in parallel; you snip a few of them and the overall spring constant is reduced. Or another way to think of it: Imagine you had a reed of a given width and then added mass to the end by making it wider at the non-attached end. You'd expect the frequency to go down.
I'm sometimes tuning accordions, which is rather similar, but if you want to lower the tone by a lot, you can plop some solder close to the tip of the reed.
It's pretty clear why that's the opposite of filing off material close to the tip, so obviously the tone goes lower.
In my mental image, filing close to the base of the reed gives the reed a similar shape as putting extra material next to the tip (thinner at the base, thicker next to the tip), and that's why it behaves the same.
The solder on the tips reminds me of a doctor visit years ago. I thought I may have broken a finger, and when I got to the doctor's office I mentioned to the receptionist that I had a high-deductible (HSA-compatible) insurance plan.
The physician's assistant said, "We could send you over for an X-ray, but since you're paying out of pocket, we can start with a simple test." He pulled a contraption out of his desk drawer and asked, "Do you know what this is?"
I said, "Yeah, a tuning fork. And based on the size and those heavy weights on the tips, it must be tuned to a rather low frequency."
He said, "Yep. So we get it vibrating and then touch the base to your finger. If you have a fracture, it will hurt because of the broken bone ends jiggling against each other. Then we will go for the X-ray to get more details. If it doesn't hurt, you are good to go. Is that OK?"
"Sounds good to me!"
It didn't hurt at all, and I just had to pay for a simple office visit instead of an expensive X-ray.
You just need a small file, like a point file. Any gasheads remember those? And a single edge razor blade or the like to lift the reed.
To raise the pitch, you file the end of the reed, making it lighter so it vibrates faster.
To lower the pitch, you file near the attached end of the reed. I am not sure on the physics of this and would appreciate anyone's insight.
The specific tuning I've done many times is to convert a standard diatonic harp (the Richter tuning) to what is now called the Melody Maker tuning.
The Richter tuning was apparently designed for "campfire songs". You could just "blow, man, blow" and all the chords would sound OK.
Later, blues musicians discovered that you could emphasize the draw notes, the ones that are easy to bend to a flat note to get that bluesy sound. This is called "cross harp". For example, in a song in G you would use a C harp instead of one tuned in G.
The problem with cross harp is that the 7th is a minor 7th and you have no way to raise it up to a major 7th if that would fit your song. And the 2nd is completely missing! In fact you just have the tonic (G in this case) on both the draw and blow notes where you might hope to hit the 2nd (A). There is no A in this scale, only the G twice.
To imagine a song where this may be a problem, think of the first three notes of the Beatles song All My Loving. It starts with 3-2-1. Oops, I ain't got the 2. Just the 1 twice.
This is where the file comes in. You raise the blow 1st to a major 2nd. And you raise the minor 7th to a major 7th in both octaves.
Now you have a harp with that bluesy sound we all love, but in a major scale!