Up to a few months ago I had a regular “quote of the week” posted. These weekly quotes were mostly taken from a section that was developed for and then cut from an upcoming publication. I love quotes but have “mined” the best of these quotes already; expect quotes to be posted on closer to a monthly schedule.
Farkas felt that the aperture and aperture formation were extremely critical to the production of a great tone, and that it is something that you should be able to form well even without a mouthpiece present.
There is another component of the embouchure which we must now consider. That is the aperture formed by the lips. In a sense, it is to produce this opening properly that we form the embouchure at all. Certainly it is the focal point of the embouchure and the spot at which the production of sound and pitch originate. Around this opening are the surfaces that do the actual vibrating, so it is important that the embouchure forms this opening correctly. From years of observation, I have concluded that the most satisfactory shape is remarkably similar to the opening in the end of an oboe reed…. This opening is most apparent when the air is being pushed through it. However, the opening should be formed by the lips and should definitely exist even when the air is not flowing. Remember that this opening is formed into shape, not blown into shape.
Philip Farkas, The Art of French Horn Playing, p. 25.