I think the key to getting a thick, covered sound of an oboe reed is the shape of the inner tip layer (the funny hill hump shape). For example if you make it wider and rounder, covering more surface area, it will sound thicker, but will also have more breath resistance. So how do you compensate for the resistance? You scrape the heart flat in a parallel manner as the Mack school teaches. But doesn’t this leave the reed a bit buzzy? Yes, so you have to scrape more out of the windows to make the heart proportionately correct. But doesn’t this lower the pitch more? Yes, so you push more reed into the mouth.
The peculiar reed I made the other day was no longer peculiar when I went and picked it back up. The back was quite large, producing a larger opening than was comfortable. Furthermore, the thick tip didn’t give me the response I wanted while playing on the tip (but I could shove it into my mouth more, putting the fulcrum closer to the back of the heart/meeting of the windows, thus “pushing” down the opening with lip pressure (i.e. biting) thus getting the response and resonance necessary out of it. But I didn’t want to do all of that, and still prefer to play on the very end of the tip. So I thinned the tip, and scraped the heart to close the reed down, which left the heart proportionally too thick, so I ended up having to scrape that, eventually wearing it down until it had the correct opening, response, etc. By then, it was just another typical Philly style reed.
I realized that a major thing in my embouchure has changed since I’ve come back to oboe; I play WAY on the tip. In fact, I think I play about as close to the tip as anyone can.
Why I say this is I’ve gotten occasional comments from oboists where they’ve picked up a reed and said. “Hey, this has a chirp!” And they go on to tongue 16th notes, all with a loud, distinctive chirp to it. Then I pick it up and tongue 16th notes, and there’s no chirp. Chirps which are audible while tonguing usually come from an imbalance in the tip, or a fluke thin spot in the tip that is somewhere in the middle of the tip. They’re quite common, usually not audible from a distance (but annoying to the oboist), and awfully hard to get rid of once they’re there. However, if you play on the extreme tip, your lips often cover the tip, and adding enough padding to cover the chirp. Occasionally it might come out, but usually not.
I remember when I was in college I frequently struggled with chirpy reeds. I don’t think my knife technique is a whole lot better now than it was then, I just think I play closer to the tip.
All oboists have chirps though. I remember hearing Mack play on a chirpy reed. Even on Zupnik’s etudes CD, you can hear that one of the reeds she recorded on had a chirp in it that came out every so often. I think learning to play closer to the tip has given me a lot of help, but this is certainly a biggy.