Mellow FM by Autosuggestion
Oscillator 2 modulates itself: try it an octave above or below 1 in addition to unison. LFO slowly modulates the Delay Time with Feedback cranked up.
Note: Audio-rate frequency modulation usually makes pitch unstable! On my machine at the moment. I've had to move Oscillator 2 about 3 semitones below Osc 1 to actually get them back in unison. You might have to do some similar pitch wiggling once you dial up the FM through Attenuator 2.