The Yamaha AN1x Synthesizer mailing list

Jim,

>One thing...and this is embarrasing to ask, but when you say vibrato...I 
>think there are more than one paramter that can produce vibrato, am I right?
>
>Which is the most common, or can you give any examples of different ways 
>to acheive controllable vibrato (i.e. where one can make it deeper, or 
>vary more, etc.)

For the most part, vibrato refers to frequency modulation only; i.e. 
modulating the pitch of the VCOs with an LFO.  This is the classic "organ" 
approach to vibrato -- all FM, no AM.

On acoustic instruments, however, the act of bending the pitch, especially 
quickly, often ands other modulations to the sound.  As an example, when a 
saxophonist creates vibrato, it's done by pulsing the mouth pressure on the 
reed, which has an effect on overall volume (AM), as well as causing 
changes the shape of the waveform (analogous to PWM).  In addition, the 
amplitude changes cause corresponding changes in the timbre of the note -- 
more volume on a saxophone = brighter timbres.

So, we have FM (vibrato), AM (tremolo), plus waveform changes (PWM) and 
timbre changes (VCF) to contend with.  If there are enough modulation 
sources available, all four sources can be triggered:  LFO -> pitch, LFO -> 
VCA, LFO -> PWM, and LFO -> VCF.

As a rule, adding VCA tremolo tends to make the vibrato "deeper", as does 
PWM modulation.  The amount of each type added will vary from sound to sound.

Regards,

-BW

--
Bruce Wahler
Design Consultant
Ashby Solutions"
www.ashbysolutions.com
CloneWheel Support Group moderator
978.386.7389  voice
978.964.0547 fax
bruce@...