I've been on a mission for the past ?2 years? to explore a harmonica technique called "tongue switching," which is usually referred to as a "shimmer" in a traditional context. For example, you can play the following riff, and this would be a tongue switching riff.
These are pretty basic. The idea is that, with tongue switching, you can play non-adjacent notes. The innovation, if you can call it that, is the idea that at any time your mouth can cover 3-4 (?5?) holes at once... why not have all of them at your immediate disposal. The biggest difference between a tongue switching approach to the harmonica is that there is much less head movement. Phrasing takes on a whole new perspective when you have 3 different ways (tongue-block left, tongue-block right, and lip-purse) to play a single note, or a series of notes..
I was exposed to a lot of metal in college (death, tech-death, prog-tech, etc.), and the harmonica seemed like it was stuck in some rut of tradition. The only real outsider is John Popper, and his technique is so far beyond the rest of the field (in a different way, to be fair), that no one's really tried to replicate it. Well, LD Miller is as close as it gets, I guess. I don't follow the profession as much any more, so there could be some others I'm not giving credit to.
I feel a bit unique in my ideas, but I could be wrong there also. Breathing aside there are 4 basic tongue switching moves that I've discovered:
1) tongue-block left (blow/draw out of the left corner of the mouth) to tongue-block right.
2) tongue-block right to tongue-block left
3) tongue-block left to lip-purse
4) tongue-block right to lip-purse.
... of course, then you add the two breathing directions to make 8 individual moves, then the overblows and overdraws that are available at certain places on the harp, which makes for a lot more moves and a lot of necessary practice. Once you get use to the those first 4 pretty clean, then the speed depends on your breathing.
I've experimented with incorporating overblows into my tongue switching, but it's really hard and I'll wait until I master some of the simpler concepts first. Overdraws, will probably be the last thing to add. Bending is not terribly difficult, but hitting the notes with that kind of speed, power, and precision is not easy either.
I figure the best way for me to develop my ideas is to start a band, so that's what I'm trying to do up here in Boise. I need something other than a metronome and my own head to play to. Till then, i'll just keep filling out my technique. I need to start getting more into scales and modes - all in time.
Pick o' the Post: "The Beacons" by Blues Traveler on North Hollywood Shootout
Check out Popper's solo at 1:39 ... not his most super-duper, fast, note-blurring, shreddy solo, but there's something that's just very deliberate and brilliant about it. I like it.
PS Here's a video from about 1.5 yrs ago that might help get the basic concept across. My technique's developed quite a bit since then. Right now I'm using a book with harp tabs for the Blues Traveler album, Four to learn to think about the notes like John Popper does as well as to find and create exercises that cater to tongue switching. All I'm really doing now is trying to play Run Around with tongue switching where it makes sense to economize the playing that way. I'm about 2/3 thru the first solo; which I think is a bit more difficult than the outro solo, but I haven't gotten there yet.
Just after this post, I discovered a way to tongue switch between 2 ADJACENT holes. It's difficult because it amounts to a regular-ol-warble, but switching back and forth between right and left tongue-blocking on only two holes. So, instead of covering 3 holes of the harp with your mouth, you have to cover only two and develop the muscle memory to tongue switch in a tighter space.
Let's say you wanted a 4D-5D warble. Essentially, you would center your mouth over the separator between the two holes, blocking the 4D with your tongue (playing the 5D), then switching your tongue and blocking the 5D (playing the 4D), then repeat. This can get very fast, and I feel it will provide more control than having to move the harp or your head to achieve the same effect - once the muscle memory has been developed.
I just started on this the other day, so I'll see where it goes. Most of this technical development is an attempt to build muscle memory, since these are not obvious - and in many cases difficult - ways to play the harmonica. Once the muscle memory is developed, then the music can flow.