you should be able to get them to do oh's and ah's voices can be broken down into sinusoidal waves but I think that is a little ambitious for csound alone. I could be wrong though

Synthesizing speech is a pretty hefty undertaking, especially if you don't want them to sound like robots. The Csound Book includes formant frequencies for vowel sounds that are a good start. Use them as center frequencies for bandpass filters and try sending the output of the buzz opcode through them as a start. Plosive sounds like "t" and "p" and other consonants like "s" will likely involve some filtered noise. Some sounds will involve transitioning from one formant to another. For example, I've found you can get a decent "y" sound by briefly starting with an "ee" formant and quickly sliding into the next vowel sound. Like, "ee-oo" will sound like "you." The hardest part, though, is getting pitch transitions right. But I'd say you have a fair amount of research ahead of you here :-).

As for the instruments, you'll have an easier time with those. The Synth Secrets articles at http://www.soundonsound.com/sos/allsynthsecrets.htm have great techniques for making drums. Realistic cymbals are pretty tough, though. You might want to take a look at some of the physical modeling opcodes as well.

You might want to start out more simply by using samples for your drum kit sounds. Not anywhere near as interesting or flexible as physical modelling, but it would be much easier to begin with and would help you learn some Csound basics. However if you do want to get into physical modelling for percussion, my guess is that mass and spring models would be your best bet. The folks at http://www.xoxos.net/ have a couple of mass-spring percussion VSTi synths ("Mass" and "Cymbal") that are not too bad, and I would certainly like to see something similar implemented in Csound. In fact such a project is on my "To Do Eventually" list.

So to answer your question, I think what you want to do is possible, but very ambitious for a beginner. Designing a really good synthetic "singer" is still something NOBODY has accomplished (in my opinion), although there are some promising attempts out there. It would be a lot easier to just learn to sing. :)

I have to ask, what does A.S.H. stand for?