Global preset parameters effect

• Ro 3 0

  Message from Rossco_50 on …
  Hi,
  I am trying to interpret/understand an SF2 library preset I have bought. How do global preset filter and LFO values effect those set at instrument level?
  
  i have a synth present that has a sweeping filter driven by a LFO. It has the following settings:
  

  • The global filter cutoff (x) is 2.0 and each instrument has a cutoff of 19993 Hz.
  • The global Mod LFO to filter parameter is set to -13671
  • The global preset Mod LFO frequency is set at 0.01 and all voices instruments have an LFO frequency of 5 hz

  
  It seems like the effect is a sweeping filter cutoff starting at a high value (20 kHz?) and going through the full audible range at a rate of about 0.05 hz. This would suggest to me that global paramters multiply (spec says "add") the local instrument parameters, but that the preset programmer has used values which exceed the 20khz filter cutoff range and the 10 octave range of the lfo amplitude - in this case the cutoff starts at the maximum 20 khz and sweeps the max 10 octaves. Does this seem a correct interpretation?
  
  Rossco_50
• ZI 190 0

  Message from ziyametedemircan on …
  It seems that the x2 cutoff-filter value in the Preset section doesn't matter.
  But: If Modulators are not used.
  If some modulators that affect frequency are used then it may have been used for some purpose.
• Ro 3 0

  Message from Rossco_50 on …
  Thanks.
  
  It may be set at 2 to work with the
  "velocity-on" modulator, however I do think that the preset value is modifying the voice cutoff - if I change the preset value to something like 0.01 then the initial cutoff audibly moves to something in the region of 200 Hz. This is why I suspected the preset value is a multiplier for the instrument value.
  
  I am perhaps being obtuse but I struggled to get confirmation from any soundfont/polyohone/viena documentation that the preset parameters are multipliers. I guess (X) means multiply and I should have realised this.
• ZI 190 0

  Message from ziyametedemircan on …
  Most of the parameters in the Preset section (on Polyphone: those marked with an "x") work by multiplying the parameters defined in the Instrument section.
  You can download the specification here: http://freepats.zenvoid.org/sf2/sfspec24.pdf 
• Ro 3 0

  Message from Rossco_50 on …
  Thanks for confirming. I had been through the spec and there is no statement that preset values multiply, in fact the term "add" is used. I realise some do add and X is clear now - think I was just confused by the values in the specific preset I am looking at which made it difficult to understand.

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