Viagra jokes are SOOOO 2001.

I would have to say no to that one. A computer could be used to modify other instruments' sounds, but it does not have its' own unique sound, and you cant really compose music for a computer to play.

Er... yes you can.

Orly?

Well i haven't been to a computer concert in a while, forgive me for my incompetence

You may want to be a little more specific with your terminology then...
Compose = create, arrange, etc. in the sense Janszoon was talking about.
Sort of like "composing a letter". And while I haven't been to a letter concert in a while....

I'm not really sure what going to a concert has to do with whether or not one can compose music for a computer to play.

I've been composing music on computers since i was about 14, and countless artists have composed music on computers over the years as far back as 1951 believe it or not, so yes it is very much possible. A computer doesn't strictly have it's own unique sound but an infinite number of sounds can be created with a computer by using different types of software.

This article might interest you:

A brief history of computer music | MusicRadar.com

Good post man, midi seems to account for 90% of computer made music. At least it used to.

In response to the title, yes a computer is an instrument.

I /know/ this, I am the musical-instrument /authority/ around here, don't mess with me :>

So... what other instruments do you use? Why didn't you post more about those before making proclamations of being the new authority around here?