TempoClock.default.tempo = 1;

SynthDef(\fmbass, { |out, amp=0.1, freq=440, index=1, modratio=2, attack=0.0001, sustain=0.01|
    var snd, mod;
    mod = freq + SinOsc.ar(freq/(modratio*Rand(0.99, 1.01)), 0, Line.ar(index, 0, sustain));
    snd = SinOsc.ar(mod);
    snd = snd * PinkNoise.ar(0.02,1);
    snd = snd * EnvGen.ar(Env.perc(attack,sustain), doneAction:2);
    OffsetOut.ar(out, snd*amp!2);
}).add;

Pdef(\bass, Pbind(
    \octave, 4,
    \index, Pseq(100.partition(8) * 25, inf),
    \modratio, Pstutter(8*4, Pxrand([1,1.5,2,3,4], inf)),
    \instrument, \fmbass,
    \sustain, 0.25,
    \amp, 0.25,
    \dur, Pseq([1]/8, inf)
)).play;