I found the following quote on the internet. Has anyone read the full article or know what it means? I don't know what under or over the windway means. The article is about 38 years old, no doubt plastic recorders have improved in this time, possibly beyond the point where such devices would make an improvement.

Fader, Bruce, and Raoul J. Fajardo “Improving the Tone of Plastic Recorders." American Recorder 12, no. 2 (May 1971): 41-43.
A soft material (fiberglass, foam, felt, balsa wood) positioned over or under the windway of a plastic recorder will effectively suppress harsh overtones. Describes how to construct several devices based on this principle to help improve the shrill strident tone produced by many plastic recorders.

The windway is the slot you blow through. Take a look at this Wikipedia entry for a diagram. I would assume that if you were to oit a layer of something in the windway you would need to remove some materail from the top of the block in order to keep the windway height the same.

Seems like a waste of time to me. There are plenty of perfectly decent sounding plastic recorders around. I have a Zen-on Stanesby soprano and Zen-on treble which are both quite pleasant and a Mollenhauer Swing which feels nice and sounds quite smooth, but has a slightly odd mouthpiece shape.

I very much doubt you could do anything to the tone of plastic recorders: and if it's a big instrument, you'd be risking a fair amount of cash invested if you tried and damaged it....

I assumed it meant how nicer-sounding plastic recorders could be manufactured as opposed to a DIY improvement. I'd have thought it would make a slight difference to the sound and might stop them fugging up quite so much. (or maybe it's just my plastics that are prone to that.)

My daughter's current specialist Recorder teacher suggested we bought her two plastic recorders. I also heard they are used at NYRO residentials.

I read about a company that were supplying the better quality Zen-on plastic recorders with some kind of cedar wood adjustment to them...? I think it was an article from the same source material. I tried to find out some more just out of curiosity, but the gentleman that was doing it is now retired...

It sounds like they probably have a wooden block. The man at Mollenhauer said they use cedar to make their blocks when I was trying to get my old one fixed. He was trying to get me to buy an (apparantly not) plastic synpor block instead.

Melt them down and use them as keys for a decent electronic keyboard, perhaps....