func main() {
ctx := sound.DefaultContext
/*
seq := sound.NewSequencer(ctx)
f0 := 110.0
seq.Add(0, KarplusStrongSaw(ctx, f0*1.00, f0*1.00 * 16, 0.98))
seq.Add(time.Second*12/40, KarplusStrongSaw(ctx, f0*1.25, f0*1.25 * 16, 0.98))
seq.Add(time.Second*24/40, KarplusStrongSaw(ctx, f0*1.50, f0*1.50 * 16, 0.98))
seq.Add(time.Second*36/40, KarplusStrongSaw(ctx, f0*2.00, f0*2.00 * 16, 0.98))
seq.Add(time.Second*37/40, KarplusStrongSaw(ctx, f0*2.50, f0*2.50 * 16, 0.98))
seq.Add(time.Second*38/40, KarplusStrongSaw(ctx, f0*3.00, f0*3.00 * 16, 0.98))
seq.Add(time.Second*39/40, KarplusStrongSaw(ctx, f0*4.00, f0*4.00 * 16, 0.98))
stream := seq.Play()
*/
stream := KarplusStrongSaw(ctx, 100.0, 1000.0, 0.98)
stream = filter.RC(ctx, stream, filter.LowPass, 300.0)
stream = ctx.TakeDuration(stream, time.Second*3/2, false)
stream = ctx.MulInf(stream, ctx.Const(0.1))
frontend.Main(ctx, stream)
}
// input should be finite and preferably short (e.g. one cycle of a triangle wave)
func KarplusStrong(ctx sound.Context, input chan float64, delaySamples uint, cutoff float64, decay float64) (output chan float64) {
feedback := make(chan float64, ctx.StreamBufferSize)
// Mix the input with the feedback.
output = ctx.Add(input, feedback)
// Fork off a copy of the output.
output, outputCopy := ctx.Fork2(output)
// The copy is first passed through a delay line...
outputCopy = delay(ctx, outputCopy, delaySamples)
// ...then filtered...
//outputCopy = filter.Chebyshev(ctx, outputCopy, filter.LowPass, cutoff, 0.5, 2)
outputCopy = filter.RC(ctx, outputCopy, filter.LowPass, cutoff)
// ...and finally attenuated slightly.
outputCopy = ctx.Mul(outputCopy, ctx.Const(decay))
// The filtered output copy is fed back into the system.
go pipe(outputCopy, feedback)
return output
}