Make 2 user waves of differing lengths - the differing lengths will cause their "innate" pitches to be different.
Load them in DoubleDraw and LFO modulate the mix back and forth. You will get this morphing wah-wah'ing sound for 8x speed.
I like to do this with userwaves that are set up to have lengths that are multiples of each other. Then they will sound harmonically related, like an octave apart or something. But that's just me - I'm only just a little arndmo