Yamaha PLG150-VL - Manual (Page 34)

34
Q & A
1 Some voices sound as if they are in the original octave even when
shifted down an octave.
This is because Virtual Acoustic synthesis accurately simulates the acoustic
behaviour of a pipe or string. Simply stated, the harmonic balance of the voice
when played in the normal octave is retained even when the voice is shifted down
an octave. The change in timbre can be greater or less, depending on the selected
voice.
2 Portamento doesn't produce smooth effect on some voices.
Trumpets and some other brass instruments tend to exhibit this phenomenon more
than others. In a VA tone generator portamento is produced by lengthening or
shortening the instrument's pipe. A trumpet is designed to emphasize the “modes”
of the pipe(s) to produce notes over a wide range using only three valves. When
portamento is applied to a trumpet voice, the pitch tends to jump from mode to
mode, thus producing the observed glissando effect. The same effect occurs with
some flute voices. Saxophone modes are not nearly as strong as trumpet modes,
but some sax voices do have two definite modes which, when spanned by a porta-
mento slide, can produce irregularities.
3 The filter, EG, and other parameters have more effect on some voices
than others.
Most voices use the low-pass filter type, but some use the bandpass or high-pass
type. Some voices use very little filter processing at all. Changing the filter settings
may not produce a particularly noticeable effect. Also the Breath Noise, Throat For-
mant, Growl, Harmonic Enhancer and Pitch EG parameter settings cannot have a
significant effect on some voices.
4 Some bowed string instrument voices tend to “squeak.”
As anyone who has played (or tried to play) a real violin knows, these instruments
naturally tend to squeak if not properly controlled. The same occurs with VA syn-
thesis. As with a real bowed string instrument, bow speed and pressure must be
properly controlled to produce the desired sound. Bow speed is usually controlled
either via breath control or an expression pedal. Bow pressure is controlled via
control number 13: “64” is medium pressure, lower values produced reduced bow
pressure, and higher values produce increased bow pressure.