Mellotron-choir on the Virus KB
 

I have worked a bit on a Mellotron-choir patch for the Virus KB lately. It has some certain Mellotron-feel over it, but it could need a some more high frequencies, but thats difficult to do due to the filter settings. Here are some samples of it:
http://home.online.no/~per-kr/Stuff/..._TheBeyond.mp3
http://home.online.no/~per-kr/Stuff/...r_Oxygene2.mp3

choir
 

Nice, are those made of spectral waves
I like wave 15,42,45 for choir sounds :D

Yes, spectral waveforms only. I've used 10, 16 and 38. I tried 45 for female choirs, but found out that 16 sounded slightly better :)

This lacks the transparency of mellotron. Now it just sounds like a string machine of some sort. Add a bit more resonance to get the sound thinner and sharper also try to add some filter stage distortion.

Nope, adding more resonance just makes the sound more screamy and bad for the ear, and adding any kind of distortion makes it sound worse. I definitively don't think this sound like a string-machine :?

But now it's too beefy to be a mellotron. It needs something to thin it out. You could also try out HP filter and/or constant phaser.

It has that analog feel of a string machine..

If you want to thin it out more, you can always try using the Phaser in 'static' mode - i.e. Rate = 0, Depth = 0.

All the other parameters (Frequency, Stages, Spread and Feedback) can then be used to change the frequency content of the sound.

I ran one of those samples through the Phaser on my Virus, and experimented with this technique - this sound is certainly very reponsive to it.