There’s a horn player (Ib Lansky-Otto, Principal Horn of the Stockholm Philharmonic) who wrote a great article on this topic, but it is no longer available online (Horn Call, Volume XXXIII No. 2 – Feb. 2003
). I’ll do my best to relate this concept. Clearly others have hit on the big issues here (hearing the pitch clearly in your mind and playing to the resonant center of the individual notes that you are playing). I agree with all of this, but for you to get to the point to understand it really well, accept it, and incorporate it into your playing, this perspective may be helpful.
The horn player (Lansky-Otto), said that for his entire playing career (many years with a big orchestra) he would strive for the darkest sound possible. The problem with this is that the sound that appears to be “dark” to the listener is actually a very dull sound that does not project well into the hall, and is very different than what the player wants the listener to hear. This dull quality is typically the result of playing above the resonant center of the individual notes on the horn and for the instrument to be in tune, the tuning slide must be pulled out.
Now this is the part that I really found interesting in this article…
There is a certain comfort zone when playing to the high end of the “slot” for each note. For horn players, especially in the upper register, the notes are so close to each other in the harmonic series that almost any pitch can be played with any finger combination. The high end of the notes (versus the resonant center where the note has vibrancy (lots of overtones) and will ring to the back of the hall), will aid in the security of attacks in this register of the horn.
When the player becomes accustomed to this “feel”, it becomes a very dominant aspect of the players sound production concept. In fact, once you play your tuning pitch and hear that you are high, this will be the pitch that locks in your head. You will pull your slide out (all the time remembering the sound in your head of the last note that you played), and you will play again with the “feel” taking over causing you to move even higher into the note slot (WAY above the resonant center of the note). You probably have pretty good pitch and will match the last note played, but now it’s the same sharp note that you played the first time, only requiring more effort and with a different sound quality.
Moving to the resonant center for each note will require some adjustments to your physical approach to sound production. You will hear the sound as being brighter when you play in the resonant center. You will also have to abandon that “feeling of security” that the horn player describes in his article (I really wish I could provide a link to it for you). This middle of the road approach to sound production may be somewhat scary at first because you will not have the reference points that you have grown accustomed to. It is well worth the effort though, and there is lots of guidance on this site to help you answer many of the questions that you will encounter.
Read about pitch center, work some breath attacks into your daily playing, “let” the sound out, model great players, etc.
If you can’t tell (while I’m writing about a horn player that described his own playing scenario), I battled with this same problem for years myself. It’s been five years since I cracked the code to finding a vibrant ringing sound. You can too!