func genMelodyArpeggio(ctx sound.Context, scale music.Scale, n int) (stream chan float64) {
var parts []chan float64
root := scale.Root
for i := 0; i < n; i++ {
if i+1 < n && rand.Float64() < 0.01 {
from := scale.Root
nextNote(&scale, root)
to := scale.Root
nextNote(&scale, root)
part := genSlideEnvelope(ctx, from, to, time.Second/4)
parts = append(parts, part)
} else {
note := scale.Root
nextNote(&scale, root)
part := ctx.TakeDuration(ctx.Const(note.Frequency()), time.Second/8, false)
parts = append(parts, part)
}
}
return ctx.Append(parts...)
}
func FrequencyEnvelope(ctx sound.Context) (stream chan float64) {
var parts []chan float64
for _, note := range Notes {
part := ctx.TakeDuration(ctx.Const(note.Frequency()), NoteDuration, false)
parts = append(parts, part)
}
return ctx.Append(parts...)
}
func FilterFormant(ctx sound.Context, input chan float64, centre, q, gain float64) (output chan float64) {
lowerCutoff := (centre - (centre / q)) / 0.772
upperCutoff := (centre + (centre / q)) / 1.29
input, formant := ctx.Fork2(input)
formant = filter.Chebyshev(ctx, formant, filter.HighPass, lowerCutoff, 0.5, 2)
formant = filter.Chebyshev(ctx, formant, filter.LowPass, upperCutoff, 0.5, 2)
formant = ctx.Mul(formant, ctx.Const(gain-1.0))
return ctx.Add(input, formant)
}
func playBassSynth(ctx sound.Context, freqInput chan float64) (stream chan float64) {
return ctx.Add(
ctx.Mul(
ctx.Square(
freqInput,
ctx.Const(0.8),
),
),
)
}
func Generate(ctx sound.Context) (left, right chan float64) {
stream := ctx.TakeDuration(
ctx.Mul(
ctx.Sine(
FrequencyEnvelope(ctx),
),
ctx.Const(0.7),
),
NoteDuration*8,
true, // Wait for a zero crossing
)
return ctx.Fork2(stream)
}
func Generate(ctx sound.Context) (left, right chan float64) {
treble := SequenceTreble(ctx).Play()
bass := SequenceBass(ctx).Play()
trebleLeft, trebleRight := ctx.Fork2(treble)
bassLeft, bassRight := ctx.Fork2(bass)
left = ctx.TakeDuration(
ctx.Add(
ctx.Mul(trebleLeft, ctx.Const(0.3)),
ctx.Mul(bassLeft, ctx.Const(0.4)),
),
NoteDuration*NumBars*3+time.Second*2,
true,
)
right = ctx.TakeDuration(
ctx.Add(
ctx.Mul(trebleRight, ctx.Const(0.4)),
ctx.Mul(bassRight, ctx.Const(0.3)),
),
NoteDuration*NumBars*3+time.Second*2,
true,
)
return left, right
}
func PlayBassNote(ctx sound.Context, freqInput chan float64, duration time.Duration) (stream chan float64) {
return ctx.TakeDuration(
ctx.Add(
ctx.Mul(
ctx.Square(
freqInput,
ctx.Const(0.8),
),
),
),
duration,
true,
)
}
func SequenceBass(ctx sound.Context) (seq *sound.Sequencer) {
melody := GenerateBassMelody()
seq = sound.NewSequencer(ctx)
var pos time.Duration
for i := 0; i < NumBars; i++ {
if rand.Float64() < 0.05 {
freqInput := ctx.Const((<-melody).Frequency())
note := PlayBassNote(ctx, freqInput, NoteDuration*3)
seq.Add(pos, note)
} else if rand.Float64() < 0.05 {
freqInput1, freqInput2 := ctx.Fork2(ctx.Const((<-melody).Frequency()))
note1 := PlayBassNote(ctx, freqInput1, NoteDuration)
note2 := PlayBassNote(ctx, freqInput2, NoteDuration)
seq.Add(pos, note1)
seq.Add(pos+NoteDuration*2, note2)
} else {
freqInput := ctx.Const((<-melody).Frequency())
note := PlayBassNote(ctx, freqInput, NoteDuration)
seq.Add(pos, note)
}
pos += NoteDuration * 3
}
return seq
}
func SequenceTreble(ctx sound.Context) (seq *sound.Sequencer) {
melody := GenerateTrebleMelody()
seq = sound.NewSequencer(ctx)
var pos time.Duration
for i := 0; i < NumBars*3; i++ {
var freqInput chan float64
var duration time.Duration
if rand.Float64() < 0.01 {
from := (<-melody).Frequency()
to := (<-melody).Frequency()
freqInput = ctx.LinearEnvelope(
from,
NoteDuration*1/5,
from,
NoteDuration*8/5,
to,
NoteDuration*1/5+time.Millisecond,
to,
)
duration = NoteDuration * 2
} else {
freqInput = ctx.Const((<-melody).Frequency())
duration = NoteDuration
}
note := PlayTrebleNote(ctx, freqInput, duration)
seq.Add(pos, note)
pos += duration
}
return seq
}
// 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
}
func playMelodySynth(ctx sound.Context, freqInput chan float64) (stream chan float64) {
freqInput1, freqInput2 := ctx.Fork2(freqInput)
return ctx.Add(
ctx.Mul(
ctx.Square(
freqInput1,
ctx.Const(0.5),
),
ctx.Const(0.75),
),
ctx.Mul(
ctx.Saw(
ctx.Mul(freqInput2, ctx.Const(2)),
),
ctx.Const(0.25),
),
)
}
func PlayTrebleNote(ctx sound.Context, freqInput chan float64, duration time.Duration) (stream chan float64) {
freqInput1, freqInput2 := ctx.Fork2(freqInput)
return ctx.TakeDuration(
ctx.Add(
ctx.Mul(
ctx.Square(
freqInput1,
ctx.Const(0.5),
),
ctx.Const(0.75),
),
ctx.Mul(
ctx.Saw(
ctx.Mul(freqInput2, ctx.Const(2)),
),
ctx.Const(0.25),
),
),
duration,
true,
)
}
func KarplusStrongSaw(ctx sound.Context, frequency, cutoff, decay float64) (output chan float64) {
delaySamples := uint((1.0 / frequency) * ctx.SampleRate)
wave := ctx.Saw(ctx.Const(frequency))
input := ctx.Take(wave, delaySamples, true)
return KarplusStrong(ctx, input, delaySamples, cutoff, decay)
}
func Generate(ctx sound.Context) (left, right chan float64) {
rand.Seed(time.Now().UnixNano())
melodyParts := make(chan chan float64)
bassParts := make(chan chan float64)
go func() {
for {
var octave int
x := rand.Float64()
if x < 0.3 {
octave = 4
} else {
octave = 5
}
root := music.MakeNote(music.D, octave)
scale := music.Scale{Root: root, Intervals: music.HarmonicMinor}
var n int
x = rand.Float64()
if x < 0.2 {
n = 3
} else if x < 0.4 {
n = 6
} else if x < 0.6 {
n = 12
} else if x < 0.8 {
n = 18
} else {
n = 24
}
melodyParts <- genMelodyArpeggio(ctx, scale, n)
}
}()
go func() {
for {
var octave int
x := rand.Float64()
if x < 0.3 {
octave = 3
} else {
octave = 2
}
root := music.MakeNote(music.D, octave)
scale := music.Scale{Root: root, Intervals: music.HarmonicMinor}
var n int
x = rand.Float64()
if x < 0.2 {
n = 3
} else if x < 0.4 {
n = 6
} else if x < 0.6 {
n = 9
} else if x < 0.8 {
n = 12
} else {
n = 18
}
bassParts <- genBassArpeggio(ctx, scale, n)
}
}()
melody := playMelodySynth(ctx, ctx.AppendStream(melodyParts))
bass := playBassSynth(ctx, ctx.AppendStream(bassParts))
melodyLeft, melodyRight := ctx.Fork2(melody)
bassLeft, bassRight := ctx.Fork2(bass)
left = ctx.TakeDuration(
ctx.Add(
ctx.Mul(melodyLeft, ctx.Const(0.4)),
ctx.Mul(bassLeft, ctx.Const(0.6)),
),
time.Second*300,
true,
)
right = ctx.TakeDuration(
ctx.Add(
ctx.Mul(melodyRight, ctx.Const(0.6)),
ctx.Mul(bassRight, ctx.Const(0.4)),
),
time.Second*300,
true,
)
return left, right
}
func genBassArpeggio(ctx sound.Context, scale music.Scale, n int) (stream chan float64) {
var parts []chan float64
root := scale.Root
for i := 0; i < n; i++ {
note := scale.Root
nextNote(&scale, root)
if rand.Float64() < 0.05 {
part := ctx.TakeDuration(
ctx.Mul(
ctx.Const(note.Frequency()),
ctx.Add( // Add a slight vibrato effect
ctx.Mul(
ctx.Sine(ctx.Const(24)),
ctx.Const(0.01),
),
ctx.Const(1.0),
),
),
time.Second*3/8,
false,
)
parts = append(parts, part)
} else if rand.Float64() < 0.05 {
part1 := ctx.TakeDuration(
ctx.Const(note.Frequency()),
time.Second/8,
false,
)
part2 := ctx.TakeDuration(
ctx.Const(note.Frequency()),
time.Second/8,
false,
)
parts = append(parts, part1)
parts = append(parts, ctx.TakeDuration(ctx.Silence(), time.Second/8, false))
parts = append(parts, part2)
} else {
part := ctx.TakeDuration(
ctx.Const(note.Frequency()),
time.Second/8,
false,
)
parts = append(parts, part)
parts = append(parts, ctx.TakeDuration(ctx.Silence(), time.Second/4, false))
}
}
return ctx.Append(parts...)
}