• Pro Tools First Pitch Shift

If you have access to 192k recording it's great. @tim prebble blogged about not so long ago. I believe this will make any plugin sound better, rather than a plugin making your sound good;)The sounds feel livelier, probably simply because higher frequencies (even the ones you don't hear) are recorded with greater precision or even recorded at all. With more high frequencies in your original sound, if you pitch it down you will still have high frequencies in it and your pitched down sound will still sound natural.E.g.

You record at 48k so the higher freq captured is 24k. You pitch that down one octave (0.5) and the highest freq will be 12k. If you had a 96k recording, it'd contain freqs up to 48k. Pitched down an octave that'd give a processed sound containing freqs still up to 24k.We only hear up to roughly 20k anyway, so I guess the pitched down sound would still sound 'natural' because it doesn't seem to be lacking in the high-end. This is my interpretation.

Now, the way the others put it is: 'DSP likes higher sample rate'.As @Shaun points out in his comment below, a higher resolution file will yield better results. This is because the DSP is applied to a better defined material, therefore the process works on smaller chunks of data and the artifacts it might generate are also smaller.

Pro Tools First Pitch Shift

Smaller artifacts have greater chances to be lost during the downsampling that ends the pitch shifting process.