Overblows have a natural tendency to be slightly flat, so in order to be able to use them they have to be bent up.
Play the overblow, softly without force, and try to bend it up slowly. As you bend up the overblow further, the draw reed will vibrate further from the plate, more air is lost and therefore more air will be needed to keep the overblow sounding.
While doing this try to concentrate on keeping the blow reed choked and try not to put tension in muscles that have no influence on the pitch of the overblow. That means; keep the cheeks, lips and tip of the tongue relaxed.
Once you feel you have a good control over the pitch of the overblow practice playing it in the right pitch from the start.
Use a piano, or other sound source to check your intonation.
I find that playing tunes I have known from when I was very young are good for practicing my intonation. When I play songs I learned to sing as a child I am very aware of the notes I want to play and how they should sound.
Don't think of the notes as "hole 5 overblow" but instead hear the note you want to play in your mind before you play it.
When you have been practicing your overblows a lot, you may have gotten used to the flatness of the notes, to stop this from happening try to record yourself regularly and make sure your intonation is correct.
Anyway, take a look at this page for some opinions on overblow harps:
If you want to play TB overblows, go for it. they can be played and with some work you can probably play them as fast as any note. Don't let the idea that something isn't possible stop you from trying it anyway.
I seriously have my doubts about people's claims of OB + TB proficiently.
As far as I've heard Dennis Gruenling for instance, he doesn't OB that much, so I suspect it's a matter of mixed embouchure rather than pure TB.
I use mixed embouchure constantly - rapidly switching between TB and pucker.
My 2 cents...
and pucker is still a bit unnatural for me. So I can OB 5-6 holes with TB very easy bend it and use it. But lower or higher stil not )):
I've been practising it a bit on my whole tone harp, so every key I mention can be compared to an overblow on hole 1.
(The blow notes of the whole tone start with a low E, then Ab, C, E, Ab etc., and all have a draw note a whole step up).
Strangely enough I have no problems doing them tongue blocked with the LEFT side of the mouth on C, E, Ab and C again.
The right side is more problematic, and will work only on C and E.
"Regular" overblows work on all 10 holes ofcourse.
I invited Dennis Gruenling to this discussion (he's gone for a few days though) also, since he's the only one I know of that plays TB-OB's; could get very interesting.
I never tongueblock in normal playing so I can't really say if it is practicle or not to play overblows with tongue block, but I do think that with a little practice it is perfectly possible to play overblows as well as, and maybe better than with a pucker.
A discussion on Harp-L showed there are just a handfull of people on the planet using them.
I started practising them this week as an experiment, but doubt very much that a high level of this technique is possible, compared to pucker overblows.
(Tongue blocking ofcourse does have many other benefits in "regular playing", I know)
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