Yamaha MU100R MU100R Owners Manual - Page 190
Problem, Possible Cause and Solution
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Troubleshooting Problem Possible Cause and Solution About VL Section 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. Portamento produces more of a glissando 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 or string and changing the Embouchure. A trumpet is designed to emphasize the "modes" of the pipe(s) to produce notes over a wide range using only three valves. When portameto 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 portamento slide, can produce irregularities. 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, high-pass, or band eliminate types. Some voices use very little filter processing at all. Changing the filter settings may not produce a particularly noticeable effect. Also the internal Breath Noise, Throat Formant, Growl, Harmonic Enhancer and Pitch EG parameter settings can have a significant effect on how much the parameters accessible via the VL section controls actually affect the sound. Some bowed string instrument voices tend to "squeek". As anyone who has played (or tried to play) a real violin knows, these instruments naturally tend to squeek if not properly controlled. The same occurs with VA synthesis. As with a real bowed string instrument, bow speed and pressure must be properly controlled in the VL section 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. Pitch bends produced by a pitch bend wheel are not always accurate. Natural acoustic musical instruments have no "pitch parameter". Pitch is determined 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 VL section's 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 "mathematically" 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 acoustic unpredictability, precise pitch bends are not always produced. 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 section 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. The VL section 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 currrent XG format and future polyphonic 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 VLXG extension. Specifically, to switch the VL section 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 VL section therefore has a "poly" which is automatically selected when a MIDI "XG on" system exclusive message is received. Appendix 179