Voice. Most powerful and natural instrument.

Natural, yes. Powerful, certainly not.

I guess I thought my response was obviously about volume, rather than emotional expression. Of course, the human voice is the most expressive of all instruments, this goes without saying. But as far as sheer power in the sense of volume - not even close. The human voice is simply not capable of the decibel levels of brass and percussion instruments, unless of course it is electronically amplified.

Hi Kijanki - yes, I do play the French horn. I tried looking up the decibel levels of various instruments quickly, but I would have to dig deep to find it. I know I have it somewhere. Anyway, the actual decibel level possible is not always that relevant to how loud something is perceived. The ear hears the amplitude of different timbres differently. The sound power of the trombone, for instance, is many times that of the French horn, even if both are playing at the same dynamic level. The sound power of a bass drum is more than four times again that of a trombone. And of course, the sound power of all of these instruments exceeds that of the voice. They can also sustain their maximum volumes for a longer period of time, especially in the case of percussion, where they don't have to stop to breathe, and are using much stronger muscle groups to play. Only if we are talking about a relatively short period of time (a long high note at the end of an aria, say) would the unamplified voice be perceived as loudly as a brass instrument, regardless of the actual decibel level.

Hi Frogman - as usual, you are correct. Indeed, I have had that experience many times myself with opera. I had been thinking more along the lines of an audience perspective. Even opera voices sometimes have difficulty carrying to the back of the hall, though not of course at the Met, where they have the very highest caliber, and a very well designed hall. However, even the average opera voice is not remotely comparable to the average human voice - the average jazz, folk, or pop singer relying on amplification would be incapable of such amplitude. It takes very well trained voices indeed to reach those volumes. I suppose the sound power of such a voice could indeed exceed that even of a trombone, though I doubt it would approach the bass drum. Unfortunately, my reference only gives the relative sound power of the orchestral instruments, not including the voice.

Kijanki, the very top professional orchestras (perhaps 15 or so in the US) will employ 6 horn players. Many others will employ 5, and almost all will employ 4. A great deal of the orchestral/opera/ballet rep calls for four horn parts. Their location on stage or in the pit varies quite a bit from orchestra to orchestra, but is usually towards the back, often in the very back. It also depends on the space. The placement of the horn section is always an acoustical issue, due to the fact that our bells point "the wrong way."

As far as decibel level compared to the trumpet, the horn is capable of more decibels, but the trumpet's sound power is slightly higher, because of the higher register. That is a good example of how our perception is involved.

As far as how hard is it to blow, it does take considerable physical effort. Learning to use the airstream (involving particularly the muscles of the diaphragm) properly is only part of it, however - there are also the muscles of the lips, which are as highly developed as any set of muscles a professional athlete would use. In general, all musicians are using much weaker muscle groups than athletes, putting just as much stress on them, and they have to last us for much longer careers. Very few brass players make it through their careers without major "chop problems" at some point. Though usually it is just a case of fatigue resulting from overuse, small tears or even nerve damage can result, and these type of injuries can end careers. I have unfortunately had several close friends that this has happened to.