[sdiy] Dumb PWM question

[jbv]

please correct me if I'm wrong, but could PWM on triangle/sine/saw
be obtained in a simpler way by FM modulation of 1 vco by the square
output of another vco (hard synched with the 1st one) with PWM ratio
different than 50% ?
    http://jbv.silences.club.fr/sdiy/PWM_example1.jpg

problems with precise amp adjustment of each half of the square period
would probable arise though...

JB