There’s this thing an Uilleann bagpipe can do, commonly called “auto-cran”, but also sometimes called “warble” or “gurgle”. When you hit the low D, you get this rapidly pulsing sound that’s difficult to listen to for long. More specifically, I would characterize it as sounding like it’s bumping up against jumping octaves, then running out of oomph to get there, and coming back down, over and over. I guess it’s not dissimilar to FM synthesis with the driving oscillator running at 6-12Hz.
I’ve spent quite a while trying to deal with this. Fixes suggested by David Daye in the book he mailed along with the pipes are:
- cram something up into the bottom of the chanter, to constrain the airflow coming out the bottom. He suggests an O ring or a U-shaped bit of material, and provides some 0.34mm polystyrene sheeting bent into a U shape for this purpose. Incidentally, this is the same material he uses to make reeds for the drones, which I found very clever.
- Sanding the reed gently (this is permanent)
- Removing material from the reed (this is permanent)
I had a fair amount of success jamming the reed open with the bridle, but that made the instrument so hard to play that the drones kept shutting off. Playing around with material at the bottom of the chanter didn’t do much.
I was steeling myself to modify the reed last night, when I found a post on the Chiff and Fipple forums suggesting opening the bridle to prevent it from pressing against the center of the reed. The poster suggested slipping a fingernail under the bridle and gently bending it out a bit. Then someone else makes the inevitable no-content “you are an idiot” post, like fanboys everywhere.
Opening the bridle has made a tremendous difference for me! After just two such adjustments, and the removal of the U-shaped thing in the bell, the gurgle is completely gone. I realized the thing was supposed to help with the gurgle, but I suppose it just goes to show that this instrument is complex!