creating a choir library

First you need to get a sampler. Sonar does not come with one. Gigasampler is a popular one. You need a VSTi sampler plug-in. Then you need a choir and some microphones to record the samples and a lot of time. Its a LOT of work. You'd be better off looking for a good Choir plug-in package. Magnus Choir is one, but I know nothing about it. There is a demo. Do your homework before you plunk your money down. 

Well, you do not need a sampler to record a choir. Technically you do not even need a sampler to edit the recorded audio from Sonar into looped samples in some formats. You could even get away with not having a sampler to play samples in Sonar, but it would certainly make it easier to trigger the samples from a keyboard or midi file. Making a good sample from even a pristine recording can be pretty time consuming, even with the best of tools, so daveny5 is probably right about the advisability of buying a set if you just want a vocal  oooh or ahh. If you do buy a set, make sure you buy the rights to use it the way you intend. The main advantage to doing your own is that you can sample stuff no one else finds sample-worthy (buffalo farts leap to mind, but I am not sure how they would survive pitch shifting), and that you can use them any way you want once you have them.

I'm thinking about creating a small choir library, consisting mainly of oohs and aahs etc. for film music like productions. however, I yet know next to nothing about sampling. I've got a good choir and a possibility to record it. I've only got the software included in in Sonar PE 8.5. would I need additional software, and how would I have to edit the recordings so I can use my library from within Dimension Pro? any advice would be appreciated.

 
Not to discourage you in any way...
But realize that any type of current-generation sample library is going to be extremely complicated/tedious to produce.
Recording a choir and then programming the results into something like Kontakt 4 (writing custom scripts to switch articulations/designing a custom GUI/etc) is a lot of work.  Not that you can't do it... but it's a lot to absorb and do well... especially if you're new to the whole process.
Do you have access to a good room/hall to record said choir?
Do you have good mics/preamps/A/D converters to record the choir?
Do you have experience in how to best record a choir (mic placement)?
Does the Choir have excellent intonation?  If not, you're going to have a nightmare in the editing stage.
In any event, know that you're getting into a monumental project. 
I'd say easily 6+ months worth of hard work...

Yes it would be a lot of work, but there is a need for choir libraries. Symphonic Choirs is a bit difficult to use and also pricey. You might consider the pricing and what you can offer before you go forward, but I think it would be nice to have an alternative to Symphonic Choirs and Vocal Planet (which I own).
 
Paul

I'll have to side with Jim on this one. I have been recording a choir for the past 10 years and it is no easy task to get a really good sound, never mind converting it all to a sampler. I don't want to discourage you, but just know what you are in for. Again, it will be no easy task.

thanks for all the input. seems this is a lot more complicated than I thought. as some pointed out, I might give it a try just for learning's sake.

for production, it seems I should rather buy something. from what I've heard, I dig EWQL Choir, but it also looks like way more than I'll ever need. a few decent aahs and oohs would be enough. any advice which library might suit my needs?

but they wouldn't fool anyone into thinking they were human.

 
you must have missed the Grammys..

Kontakt 4 has a new Choir in the bundled library, the blurb says "The Choir collection makes use of the new Authentic Expression Technology giving you a new level of control: the choir voices can seamlessly morph the vowels ("A-E-I-O-U") while holding a key/note, "
 
Has anyone tried this? is it any good?
 
I use the MTRON pro choirs a lot. NOT realistic as a human choir, but quite organic and perfect for that early 70's prog sound. Wick Rakeman's even got his name on some of the patches.

Kontakt 4 has a new Choir in the bundled library, the blurb says "The Choir collection makes use of the new Authentic Expression Technology giving you a new level of control: the choir voices can seamlessly morph the vowels ("A-E-I-O-U") while holding a key/note, " Has anyone tried this? is it any good?

I would like to know this, too. It might be sufficient motivation to upgrade to K4.

If the OP is new to sampling, then there would be no better way to jump in than get Kontakt 4.
It's all the sampler you'll ever need... and then some.     

The K4 Choirs are ok. They've programmed them pretty nicely with keyswitches. I use them layered with other choir libraries to fill out the sound. I mostly layer them with the choir patches from Ilio Origins, which have a nice close up sound. http://www.ilio.com/ilio/origins/index.htm

Currently my favorite choir library is Bela D Media's The Giovani Edition, which has a boy choir and a girl choir. http://www.bestservice.de/detail1.asp/bela_d_media/the_giovani_edition/en

I don't know if I'd try and record a "library", but given the chance to record a choir I'd take it. Yummy samples abound with that stuff.