74 lines
1.5 KiB
Forth
74 lines
1.5 KiB
Forth
module SoundGen.Synth
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open Settings
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let getHzBySemitones semi =
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pitchStandard * (2. ** (1. / 12.)) ** semi
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let getSemitonesByNote (str: string) =
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let defaultOctave = 4
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let notes =
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[ "A"
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"A#"
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"B"
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"C"
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"C#"
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"D"
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"D#"
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"E"
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"F"
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"F#"
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"G"
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"G#" ]
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|> List.toArray
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let octave =
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str.Substring(str.Length - 1) |> int
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let noteShift =
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Array.findIndex (fun e -> e = str.Substring(0, str.Length - 1)) notes
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(octave - defaultOctave - 1) * 12 + noteShift
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let freq hz duration =
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let samples =
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seq { 0.0 .. (duration * sampleRate) }
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let attack =
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let samplesToRise =
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(sampleRate * (0.001 * attackMs))
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let risingDelta = 1. / samplesToRise
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let mutable i = 0.
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seq {
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while true do
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i <- i + risingDelta
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yield min i 1.
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}
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let output =
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Seq.map
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(fun x ->
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x
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|> (*) (2. * System.Math.PI * hz / sampleRate)
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|> sin
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|> (*) volume
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)
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samples
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let adsrLength = Seq.length output
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let attackArray =
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attack |> Seq.take adsrLength
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let release = Seq.rev attackArray
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Seq.zip3 release attackArray output
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|> Seq.map (fun (x, y, z) -> (x * y * z))
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let note semitone beats =
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let hz = getHzBySemitones semitone
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freq hz (beats * beatDuration) |