Yamaha PLG150-VL - Manual (Page 35)

35
Q & A
5 Pitch bends produced by a pitch bend wheel are not always accurate.
Natural acoustic musical instruments have no “pitch parameter.” Pitch is deter-
mined by the properties of the instrument’s resonant body as well as the condition
of the instrument’s driver. The same applies to Virtual Acoustic Synthesis: in the
pitch bend is simulated by manipulating the appropriate pipe/string length and
driver characteristics. As a result, the pitch bend range may not always be “mathe-
matically” accurate.
With reed instruments such as saxophone or clarinet, highly realistic pitch bends
are produced by controlling both pitch and embouchure at the same time. Since
the embouchure component of the pitch bend behaves with characteristics acous-
tic unpredictability, precise pitch bends are not always produced.
6 Some voices don’t respond as expected to EG edits.
The effect of editing envelope generator parameters may not always be as
expected — particularly with plucked string instrument voices such as guitar or
bass. This is because the VL actually simulates the plucking, free oscillation, and
muting of the strings rather than simply using an EG to approximate these events.
If the sound of a string voice decays naturally, for example, setting a long release
time will have little or no effect on the actual sound of the voice. Since the attack
and decay portions of the voice also have natural timbre variations, these can be
unnaturally altered by inappropriate EG settings — which is OK if you’re trying to
produce an unnatural effect. Trial and experimentation and the only sure ways to
determine how the EG parameters are going to affect a particular voice.
7 The PLG150-VL is a monophonic tone generator. Why is the “poly”
mode initialy selected when the VL-XG sound module mode is
engaged?
This is to provide compatibility between the current XG format and future poly-
phonic VL-series tone generators. It also provides a certain degree of compatibility
to allow playback of VL-XG song data on existing tone generators which do not
feature the VL-XG extension. Specifically, to switch the PLG150-VL to the mono
mode a “mono mode” command (control change no.126, value 0-16) is embedded
in the song data which, when received by a 32-note or 64-note polyphonic XG tone
generator, switches the appropriate parts to the mono mode. The same will apply
to future polyphonic VL-series tone generators, so no changes will be required.
The PLG150-VL therefore has a “poly” which is automatically selected when a
MIDI “XG on” system exclusive message is received.