You're not using the correct term. The blow bends in holes 7 thru 10 are not overblows. They're just high blow bends. An overblow happens in Holes 1 thru 6 and makes the note pop UP to a higher pitch.
You're right, though, blowing hard is never the way to get any kind of bend. It's all about shaping your vocal tract. Your discovery of getting the high notes to respond by opening up the back of your vocal tract by raising the soft palate and lowering the tongue is spot on.
You can make all notes sound better by opening up your vocal tract this way - try yawning and then holding your throat and tongue in that open position as you play. You can add some back pressure to "drive" notes, but you can do that by tongue placement no matter how softly you're playing - blowing hard is not required. However, some tongue positions will tune your mouth to a note that the reed can't respond to - that's when you get the ringing and squeals - something Oskars are particularly prone to when mouth shape is not optimal.
Bending, whether up or down, is a matter of narrowing the airflow near the back of the mouth cavity for low note, and further forward for high notes, then fine tuning the size of the mouth cavity by sliding the narrowed spot forward or back. When you're inhaling you'll feel suction and when exhaling you'll feel pressure.
Winslow
----- Original Message ---- From: G. E. Popenoe <gpopenoe@xxxxxxxxx> To: harp-l@xxxxxxxxxx Sent: Wednesday, February 6, 2008 11:43:53 PM Subject: [Harp-L] Tope register squeal on Lee Oskars
<snip>
P.S. I think I'm not liking the term "overblow." That is if I understand how
you guys are using the term. It implies to me that I must blow harder to get
the bend. To me blowing harder means I squeeze the air out of your lungs
with geater force. By contrast, getting bends for me is more like adjusting
the nozzel on my garden hose. Same amount of water pressure from the spigot,
but different shape of nozzle. The key for me is diaphram support. I must
have consistent stable foundation combined with measured air release in
order to have control in my mouth and throat for bends and vibrato.
_______________________________________________
Harp-L is sponsored by SPAH, http://www.spah.org
Harp-L@xxxxxxxxxx
http://harp-l.org/mailman/listinfo/harp-l
Never miss a thing. Make Yahoo your homepage.