To add some delayed vibrato to our chorusing instrument we use another oscillator for the vibrato and a line segment generator, linseg, as a means of controlling the delay. linseg is a k-rate or a-rate signal generator which traces a series of straight line segments between any number of specified points. The Csound manual describes it as:

kr linseg ia, idur1, ib[, idur2, ic[...]]
ar linseg ia, idur1, ib[, idur2, ic[...]]

Since we intend to use this to slowly scale the amount of signal coming from our vibrato oscillator, we'll choose the k-rate version. The i-rate variables: ia, ib, ic, etc., are the values for the points. The i-rate variables: idur1, idur2, idur3, etc., set the duration, in seconds, between segments.

instr 5	; toot5.orc
	irel	=	.01	; set vibrato release time
	idel1	=	p3 * p10	; calculate initial delay (% of dur)
	isus	=	p3 - (idel1 + irel)	; calculate remaining duration
	iamp	=	ampdb(p4)	; p4=amp
	iscale	=	iamp * .333
	inote	=	cpspch(p5)	; p5=freq
	k3	linseg	0, idel1, p9, isus, p9, irel, 0	; p6=attack time
	k2	oscil	k3, p8, 1	; p7=release time
	k1	linen	iscale, p6, p3, p7	; p8=vib rate
	a3	oscil	k1, inote*.995+k2, 1	; p9=vib depth
	a2	oscil	k1, inote*1.005+k2, 1	; p10=vib delay (0-1)
	a1	oscil	k1, inote+k2, 1
	out	a1+a2+a3
endin