Getting those great bluesy harp tones

Hello sir, 

Ive been listening  to some good recorded harp music an I begin to listen more carefully.  I hear very cool sounds which seem to sound raspy, perhaps a bit kazoo like or a almost a growl.  My tones dont approach anything like that.  I had thought it was made by cupping but Im undable to produce those hot bluesy tones.  Im wondering if these sounds show perhaps partial hole coverage ...which would be way beyound my 3 year skill level.... dont know.

Any guidance?

gary k

Again, I have to thank you for getting me off the ground on bending sometime back.  Im getting pretty decent on basic bends now and I hardly have to think of it.