We are going to make an FM pair from scratch. First we start with a modulator signal, which controls (modulates) the frequency of the carrier oscillator.
440 440 sine
This creates a sine wave that goes between -440 and 440. Next we bias it by 440 Hz so it centers 440 Hz, going down to 0 Hz and going up to 880 Hz:
Finally, we send this signal to modulate the frequency carrier signal:
What we end up with is a basic FM pair at 440 Hz, 1 1:1 Carrier-Modulator ratio, with a modulation index of 1, and an ampitude of 0.5.