I don't think Kronos allows you to modulate a signal with a other oscillator.
Pretty much all Phase/frequency/amp modulation sounds that sound good are going to sound much worse without at least over 40hz.
As Evil Dragon notes, the MOD-7 does audio-rate frequency and amp modulation/ring modulation.
The AL-1 also has audio-rate frequency and amp mod/ring mod between the two oscillators.
The MS-20EX does this sort of thing as well as other audio-rate modulation, including modulating the two filter cutoffs (LPF and HPF) with the audio oscillators.