I have a feeling that symphonic orchestras will be extinct. A few hundreds years ago so called "horn orchestras" were widespread, where each instrument, and of course the musician who was usually a slave, could perform only a single note by the command of the conductor. These instruments and orchestras disappeared with the advent of multi-note instruments of the same or better quality of sound.
Now the parallel: Today, using advanced DAW and synthesisers, a single musician can perform sounds of the best symphonic orchestras and more. Not only he can write and have the music performed automatically, he can actually play and combine the sounds of different instruments in real time using a single synthesiser...
The majority of concert composers do not use DAW or synthesizers. Most working composers that use that software are film composers who are working on low budget films that cant afford live performers.
The goal for most concert composers is to have concerts and record liver performers, synths just don't work on the stage nor do they really work on CDs. I know that is my goal as a concert composer. I dont want just a recording done by a computer, I want that performance in front of an audience, and I want multiple performances with multiple orchestras and performers.
That and the fact that nothing can beat liver performers, no matter how good a DAW and synths can sound, you can always tell the difference between live and computers generated due to the fact that live performers bring a bit of humanity to a performance.
And then there is the human interpretation, computers can not interpret phrase or a musical sentence like a performer can. A Computer only plays what it is told to do, and it will do it the same every time. No one wants to hear a live performance of the same thing over and over again played almost emotionless. I believe that composing is more or less a collaboration with performers, both learn from each other, something that can not be learned from just using samples and synthesis.
And, I dont know about you or any one else here, but I can always tell the difference from a computer imitating an orchestra from a real orchestra. I have yet to hear synth or sample that have all the sounds an orchestra can make, most lack the natural acoustics that real instruments have, or lack the extended technique that all instruments can do, and as far as I know, they still lack the full range of interpretative articulations and phrasing that real instruments can do idiomatically.
So I dont think any orchestra is worried about being replaced by synthesis, no matter how good they get, because real orchestras can still do things that synthesis and computers will never be able to do. And audiences will always prefer the real thing over computers. Concert halls dont fill up with people because of latest sample sounds. And besides, synthesizers already have a library of sounds that are idiomatic to them and only them, why would a composers not use those sounds instead?
The problem with all that is if computers were smart enough to have their own lives, they would've calculated how much of a waste of time music is, and thus refused to take part in your compositions unless you paid them an acceptable rate... which would lead us back to square one. The only solution then is to design computers to have feelings, and to love music, but then they would only want to work on their music- not yours.
The best sounds you can get from a synthesizer in regards to mimicking an orchestra are sampled performances of said orchestra. However, a snapshot of a sound doesn't work as well in any other musical context except for the one that it was recorded doing. I tell directors that using samples can sound good, but it's like taking different shots of Mel Gibson in Braveheart and trying to edit your own movie together. Sure they look great, but how can you really call it your own? Besides, orchestral instruments are all far too expressive to be controlled by a keyboard as Tyler already pointed out.
One time I hired a clarinet player to track over the sampled clarinet I currently had. Her husband remarked that the sample sounded really good and asked what the advantage was to using a real instrument. I cracked a joke saying the husband of a clarinetist shouldn't be questioning why the composer hired her. I thought for sure that nothing could top that, but the fact that a fellow composer seems to be asking the same question really surprises me. I even have a page dedicated to midi/sampled orchestral sounds versus real instruments if anyone is at all interested (I apologize in advance that the only examples I have are my own works- simply because I don't own other people's music or performances): http://www.douglasedward.com/midivsreal.htm
AndrewG- I'm guessing that you haven't had the fortune of hearing your music performed or recorded with live instruments? It honestly doesn't matter how long one spends trying to mimic an orchestra, because the moment you hear a real instrument play your piece it suddenly sounds far better. There is something to be said about hiring someone who has dedicated their life and education to one or two instruments. Experiencing it first hand with your own music teaches you more than could ever be explained.
As you mentioned Artificial Intelligence (AI), in last century Turing proposed the following test: A human operator communicates, using a computer keyboard, with either AI or another human, and needs to guess with whom he communicates. If the operator cannot tell the AI system from the human, then the AI system is considered good. (There is a long story how they deceived the operators using sub-optimal AI programs). As for pianos, I think, in a few years even trained musicians will not be able to tell the digital from the acoustic ones.
I found your AI story interesting, and in a strange way kind of familiar... I think I took that AI test over the phone... with a violist... and I couldn't tell if I was talking to a musician or a washing machine. In the end it sounded too consistent to be a viola, because their fingers are like lightening... they never strike the same place twice!
At least violists invented the minor second and the canon, even though they were really just trying to play together.
ok so I play the viola I can crack a joke or two about it haha.
as far as synths killing a live orchestra.. I just dont see that happening, there is no way a synth can compare sonically. that said I can see them being used to augment the orchestra and add new sounds and open up new worlds in live performance.
I dont know about DAW being used in only low budget stuff. refer to this link http://www.garritan.com/bravo.html
and LOL @ the violin jokes =)