I'm new in ChucK (up to now I used mainly Max and Csound). I like the language and would like to use it for my next piece, which will be for trombone and live-electronics. What I need is:
Great, let's go over the parts that you need.
1. record the live input (6 microphones)
Ok, so that will mean starting ChucK with "chuck --chanels6" to get 6 channels instead of the default 2.
in buffers and play the content back later (in parts);
The best way to do this is likely the LiSa (LIve SAmpling) ugen, in the /examples/special/ directory there is a series of examples dealing with her syntax. I suggest you start there and as soon as you get to grips with her look into the "hid" examples to tie keyboard control to your LiSa Ugens.
I've said before that I feel tieing one example that makes sound to another that deals with control input while looking up any bits you don't get in the manual is a good way to start ChucKing. That way it'll be exciting from the beginning and this need not be all that hard at all.
2. live transposition via fft (like the gizmo object in Max);
I'm not sure about gizmo but we do have FFT, there are examples in the /examples/analysis/ directory of your install. You may also want to have a look at the Uanae paper that's linked on the main ChucK site as that explains in detail how ChucK deals with analysis and re-synthesis.
3. working on partials (e.g. changing the amplitudes or selecting any).
The FFT Ugen will give you a array that consists of complex numbers, giving you the phase and amplitude of all partials. You can do arbitrary opperations on those before you pass it on to the inverse fft for re-synthesis; it works like any other array.
I think this is not very sophisticated, but after having a look in the documentation and the examples I don't know whether it can be done in ChucK, and how.
So I'd appreciate a lot if anyone can tell me where I can find some examples.
Well, I'd say it's a slightly more sophyisticated project as a first one in ChucK , after all fft and i-fft are fairly complicated operations but it's quite possible. I'd take it one step at a time, in exactly the order you already gave, base it on the examples that come with the download and ask questions as (or if) you get stuck.
As a first tip; to keep this all clean I'd use a array of 6 LISa ugens instead of defining them all one by one. This is a bit more advanced then most of the examples but it'll save you a lot of typing later on (do have a look at how arrays work as well).
--------------------
//define 6 LiSa ugens in a array called "buffers"
LiSa buffers[6];
//loop over this array, connecting each LiSa to a soundcard in and out-put.
//this is assuming you started ChucK with 6 in and outputs
for(int n; n< buffers.cap(); n++)
{
adc.chan( n ) => buffers[ n ] => dac.chan ( n);
}