The tweak as explained in the note that came with the whistle:
The Irvine tweak consists of New Tweaked Walton's Mellow D. All excess plastic left by the factory has been removed, and wind way is clear. The cavity under the wind way has been filled to add in stabilizing the tone. A new blade has been made of brass, and secured with a plastic pin. The new blade is set closer to the wind way exit to produce a softer tone, and provide a smooth surface for the air to move across. The brass also compliments the appearance of the tone tube. Walton's tone tubes are made a little short causing the bottom d to be sharp. A perturbation has been added in the tone tube to correct this and make a stronger note. The Irvine tweaked Walton's fipple has a very smooth, mellow, and stable tone.
To be honest, I have not played an untweaked Walton's mellow D, so I had to judge this whistle on it's own merit. There's a few quick pics and a sound clip below.
Here's some of my impressions. The wind-way is open, so the breath requirement is like a regular Generation. Intonation is pretty good, as good as (better than untweaked) any other whistle in this class. On this whistle, C natural plays in better tune and focus with no breath adjustment at 0XX000 than a Generation. It's warm and humid here so my fingers were a little sticky, but still the whistle is an easy player. The voice is warm, smooth, and a little breathy - like somewhere between a Generation and a Shaw.
Altogether it's a very satisfying, easy playing whistle, with a warm and mellow tone. Whomever I ship it to at the end of the fundraiser should be very pleased.
A note about the sound-clip. I am working with a new condenser mic and the coloration seems more lively than my previous mic. It's also very sensitive, so I had the input level a bit high. Maybe I need to soften the room. The tone in person is a touch less strident than the sound-clip.
http://www.beancurdturtle.com/Whistle/I ... llow-D.mp3
Do you have one? What are your thoughts? Comments are welcome!