It's tuneable, with a brass slide that's machined to perfect tolerance, i.e., adjusts easily without any hint of slippage.
As I have probably the three finest delrin high D whistles made - Abell, Busman (little green man), and Oz - I've been playing them a lot lately and comparing as much as possible. I'll avoid the overly scientific detailed stuff - you'd be pleased as punch to find any one of them in your stocking. The Oz is about as light as the Busman and lighter than the Abell, probably due to that chunky Abell mouthpiece.
It's as responsive as called for by my meager talents and has a lovely and relatively bright and pure tone. The real treat is really nice balance between octaves both in volume and tone; that is, no noticeable tradeoffs in that while the upper is strong yet sweet, the lower is strong and mellow as well.
Suffice to say I like it and will not be passing it on to absorb anyone else's er, input.
Overall well behaved and moderate in air required, backpressure, and volume. My wife prefers its tone to the other two.
And before you go thinking that all delrins are alike, I did have one once that did not have good balance and gave everyone fits trying to reach that high B without terrible squawking; all three of these present no problem in that regard.
Gotta go pack. It's mine, MINE I tells ya!
PhiloHahahahahahahahaha!
