<CsoundSynthesizer>

<CsOptions>
-dW -o spiral.wav
</CsOptions>

<CsInstruments>
	; Setup
	sr = 44100		; Sample rate
	kr = 4410		; Control rate (k-rate)
	nchnls = 1		; One channel

	; Variables
	giMax = 32767	; Maximum amplitude


	;----------------------------------------------
	; Infinite loop 1
	; This instrument outputs a down-looping sound
	; for a given period of time, with a small
	; fade-in, fade-out envelope.
	;
	; - p4 : base frequency
	; - p5 : Duration of one octave slide (seconds)
	instr 1
		iBaseFreq = p4
		iDuration = p5
		iFrequency = 1 / iDuration

		kPhase 	phasor iFrequency, 0

		kFreq1 = iBaseFreq / powoftwo(kPhase)
		kFreq2 = kFreq1 * 2
		kFreq3 = kFreq1 * 4

		kEnv1		table (kPhase + 2) / 3, 2, 1, 0, 1
		kEnv2		table (kPhase + 1) / 3, 2, 1, 0, 1
		kEnv3		table (kPhase + 0) / 3, 2, 1, 0, 1

		a1			oscil giMax * kEnv1, kFreq1, 1
		a2			oscil giMax * kEnv2, kFreq2, 1
		a3			oscil giMax * kEnv3, kFreq3, 1

		; Overall envelope
		kEnv 		linseg 0, 1, 1, p3 - 2, 1, 1, 0

		aout = kEnv * (a1 + a2 + a3) / 3
					out aout
	endin


	;----------------------------------------------
	; Infinite loop 2
	; This instrument outputs a single down-sliding
	; sinewave with an amplitude envelope, making
	; it suitable for a cascading suite of several
	; tones.
	;
	; - p4 : base frequency
	; - p5 : Duration of one three-octave slide (seconds)
	instr 2
		iBaseFreq = p4
		iDuration = p5
		
		kIndex 	line 0, iDuration, 3

		kFreq = iBaseFreq / powoftwo(kIndex)
		kEnv		table (kIndex / 3), 2, 1, 0, 1
		asine		oscil giMax * kEnv / 3, kFreq, 1
					out asine
	endin
</CsInstruments>

<CsScore>
	; Tables
	f1 0 16384 10 1		; Sinewave
	f2 0 257 20 2 1		; Amplitude envelope
	
	; Score

	; First spiral (30 seconds)
	i1 0 30 110 10

	; Second spiral (80 seconds)
	i2 35 30 440 30
	i2 45 30 440 30
	i2 55 30 440 30
	i2 65 30 440 30
	i2 75 30 440 30
	i2 85 30 440 30
	e
</CsScore>

</CsoundSynthesizer>