FIGnition FUZE Hardware Reference Manual page 26

In addition, as the pitch rises, the peak of the wave drops from +/-5v to +/-2.5v [Fig 4.6].
At high pitches, you can see that the capacitor does not instantly charge, there is a sharp
curve which becomes more gradual near the top (or bottom) of the wave [Fig 4.7].
Fig 4.5
Fig 4.6