[Harp-L] Why are some overblows easier than others?

[David Fairweather <dmf273@xxxxxxxxx>]

I think most people would agree that the #6 overblow is easier (at least
for beginners) than the #5, which is easier than the #4.   Is there a
physical explanation for this?   I just got a new Hohner Blues Harp in the
key of Ab and spent 1/2 hour trying to gap the #4 overblow.   Never really
did get a good compromise that didn't make the #4 unbent blow reed choke up
too easily.    I figured the unbent blow note was too important to risk it
choking up onstage and that I'd rarely use the #4 overblow, so I finally
gave up.   But I'm wondering why?    And does it matter what key harp
you're gapping?   Was the Ab harps #4 reed just too low?