f <- 22050
F1 <- synth(f=f, am=c(50,10), cf=2000, d=1, fm=c(500,5,0), plot=FALSE)
F2 <- synth(f=f, a=0.8, cf=4000, am=c(50,10), d=1, fm=c(500,5,0), plot=FALSE)
F3 <- synth(f=f, a=0.6, cf=6000, am=c(50,10), d=1, fm=c(500,5,2000), plot=FALSE)
F4 <- synth(f=f, a=0.4, cf=8000, am=c(50,10), d=1, fm=c(500,5,2000), plot=FALSE)
final <- F1+F2+F3+F4
spectro(final,f=f, wl=512, ovlp=75, osc=TRUE)