First sound sample from the GT1.  It's using six oscillators:
1) A sawtooth wave at the fundamental.
2) A sine wave one octave lower.
3) A sine wave at a 5/4 ratio.
4, 5, 6) All of the above, but at a 3/2 ratio.

Notes are picked randomly between 200 and 600 Hz.

There's a 220Hz lowpass (via biquad) filter, a +3 noise pop with a probability of 0.0002 per sample, and general noise between -0.2 and 0.2.

There is quadratic out easing between each note for 2 seconds, and finally an LFO in additive mode is running at 5.2Hz with an amplitude of 0.005 while glides are disabled.

Gabriel Taubman