I'll let the inventor of Paddy Richter tuning, Brendan Power, explain what it is. In this video he gives some examples of how Paddy Richter Tuning is used in Irish, Celtic, Folk and other styles of music. He also talks about the differences between a regular Diatonic Harmonica and a modified Paddy Richter Tuned Harmonica.
After watching this video you'll find that basically the difference between a regular harmonica and Brendan Power's Paddy Richter tuned harmonica is the 3 hole blow. He sells harmonica's pre-tuned to Paddy Richter and also has a instructional book on how to play Irish music on the harmonica on his website.
But if you all ready have a regular old diatonic harmonica lying around and would like to tune it yourself, it's not too hard. All you need is a small screw driver, a nail file, a receipt or folded piece of paper and a tuner. If you have an iPhone or iPad you can find free tuning apps on the app store.
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I worked out how to tune my harmonica to Paddy Richter tuning on my own by watching the next two videos. The first one is by Håkan Ehn an amazing Swedish harp player. He has a lot of experience tuning harmonicas and you'll see how to raise the pitch of the 6th hole draw harmonica reed. I took this same technique and applied it to the 3 hole blow reed for Paddy Richter tuning.
The pace of this video is a bit slow but keep with it, it's full of good subtle information. He only adjusts the pitch a little bit in this video, but for Paddy Richter tuning we will have to raise the pitch one note. It's the same technique, just filing down the tip of the reed, but it takes longer.
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This next video is by Adam Gussow, an amazing blues harmonica player and educator. This video isn't focused on retuning but it will show you how to do Paddy Richter tuning with materials you may have around the house. For instance he keeps the reed supported with an ATM receipt. That's what I used when I did a Paddy Richter re-tune on a few of my harmonicas.
The most important thing about this video is if you have a Honer Marine Band harmonica. You'll sit down to start working on it and be stumped with how to take it apart. There's no screws! Those are nails! So Adam Gussow shows you how to use a Swiss Army knife to take it apart.
If you are thinking about buying a harmonica and want one with screws, Honer's Big River and Blues Harp models are put together with screws and are easier to fiddle around with. I used these models for my two Paddy Richter tuning experiments, a Big River in D and a Blues Harp in G.