How can one person sound as a complete choir?

[Trebor]

@stevethefiddle

The choir was made from multiple copies of the first sample with changes to the pitch, speed, start time and pan position. The sustain of the note was also adjusted by editing (cut and cross-fade) to provide two versions of the voice. The whole lot was then mixed and stereo reverb (Freeverb) added.

Did something similar with a sax solo and converted it to a big band …

I used the free ANWIDA reverb VST that Irish pointed out, rather than Freeverb.
Also used “random amplitude modulation” and “random pitch modulation” plug-ins from here … http://audacityteam.org/download/nyquistplugins (in last 10 on the list) to add a bit of variation to the various copies.