Roaring

A biologically based roaring framework as provided by Weissengruber;

"We suggest that roaring (the low pitch vocalization seen in

prototypical form in lions and red deer) has two distinct

physiological and acoustic components:

1 a low fundamental frequency, made possible by long or

heavy vocal folds, which lead to the low pitch of the roar;

2 lowered formant frequencies, made possible by an

elongated vocal tract, which provide the impressive

baritone timbre of roars."

This highlights possible principles to inform the design to getting an 'accurate' roar sound.

Weissengruber, G. E. et al. 2002. Hyoid apparatus and pharynx in the lion (Panthera leo), jaguar (Panthera onca), tiger (Panthera tigris), cheetah (Acinonyx jubatus) and domestic cat (Felis silvestris f. catus). Journal of Anatomy. 201(3): pp.195-209. 

From Cough To Roar;

An interesting and amazingly short process that uses a short cough for the input sound and then time stretches it.

The result is very impressive. 

This just shows you have to experiment, and not go for the obvious "RRRRRRRRRRAAAAAAAWR!"

Will try and experiment with this in future prototypes. 

This use of pitch shifting may address altering the Source section within using the Source-Filter framework within this design. It also addresses the first condition outlined by Weissengruber's roaring framework, to produce a sound that features low fundamental frequency.
The next stage would be to do the filtering steps, looking at formants to suffice the Filter side of the theory.

In terms of utilising time stretching in MSP;

http://www.devinkerr.com/2008/10/30/free_elastic-independent-pitchspeed-control-in-max/

Another paper prototype detailing the analytical process;