Thanks for that suggestion, GSS. Such a thing can be accomplished on a hammered dulcimer with a technique called a "flam" -- basically playing a grace note with one hammer just before hitting another note with the other hammer. A flam is used with whole tones in Irish music, but there's no reason I couldn't try it with half tones to play blues.

I'd probably want to dampen the first half tone with the hammer or my finger so it wouldn't keep ringing (since I don't have dampers on my instrument). Can't help thinking that HD blues would work better on an instrument that does not have a long sustain.