From and earlier SOS article
It's A Vocoder!
PI makes a decent vocoder. I don't know why Cakewalk don't do more to promote this feature, but here's how to use it.

Each of the oscillators can use a custom waveform in addition to the 14 standard ones.
1. Do not insert
Pentagon into a track using the Insert / Soft Synth command. Instead, right-click in an audio track FX bin and go Soft Synths /
Pentagon I. We'll call this the audio/instrument track, as it has characteristics of both.
2. Create a MIDI track to drive the audio/instrument track and assign its MIDI output to
PI.
3. Assign the audio/instrument track input to your mic audio-input source (ie. from your audio interface).
4. Set the audio/instrument track Input Echo to 'On'.
5. Call up the
PI patch you want to use as the vocoder 'carrier'.
6. Click on the
PI logo and go Voice Modulator / On.
7. If you want a more 'voice-like' effect, click on the
Pentagon I logo and go Formant Filter / On.
8. Speak into the mic, play your keyboard, and voila — instant vocoder!
You're not limited to using a source plugged into a
Sonar audio input to do the vocoding. For example, one of my favorite tricks is to load a drum part into the audio/instrument track and use that to modulate whatever patch is selected in the
Pentagon I. You can also manipulate the filter, LFO, VCA and other controls while all this is playing. In fact, you can appear to 'gate' the vocoded signal by setting a short amplitude decay time on the
PI amplifier. This causes the patch sound to decay rapidly; when there's no signal left, there's nothing for the mic or other input to vocode, so you won't hear what's happening at the input.
Fred