(
SynthDef(\cowbell, {
    | out=0, amp=0.3, gate=1, fund_freq=540, pan=0.0 |
    var sig, env, hash;

    // hash = DC.ar(0);
    hash = BPF.ar(
        Hasher.ar(Sweep.ar(rate: TRand.kr(1.0, 10.0))), 
        fund_freq * 1.4, 
        0.5,
        2
    ).tanh * Env.perc(0.001, 0.02).ar(0);
    sig = Pulse.ar( fund_freq * [ 1, 1.5085 ], [ 0.565, 0.445 ], [ 0.4, 0.6 ] ).atan;
    env = EnvGen.ar(
            Env(
                [ 0, 0.05, 1, 0.1, 0 ], [ 0.003, 0.002, 0.05, 0.5 ], [2, -4, -4, -4]
            ),
        gate: gate,
        timeScale: [ 1.0, 1.5 ],
        doneAction: 2
        );
    sig = Mix( (hash + sig) * env );
    sig = BPF.ar( sig, fund_freq * 2, 1.808 );

    Out.ar( out, Pan2.ar( sig, pan, amp ) );
}).add;
)

Synth(\cowbell);