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furnace/doc/4-instrument/c64.md

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C64 SID instrument editor

The C64 instrument editor consists of two tabs: "C64" to control various parameters of sound channels, and "Macros" containing several macros.

C64

  • [Waveform] - allows selecting a waveform. NOTE: more than one waveform can be selected at once, logical AND mix of waves will be produced, with an exception of a noise waveform, it can't be mixed.
  • [Attack] - determines the rising time for the sound. The bigger the value, the slower the attack. (0-15 range)
  • [Decay]- Determines the diminishing time for the sound. The higher the value, the longer the decay. It's the initial amplitude decay rate. (0-15 range)
  • [Sustain] - Sets the volume level at which the sound stops decaying and holds steady. (0-15 range)
  • [Release] - Determines the rate at which the sound disappears after KEY-OFF. The higher the value, the longer the release. (0-15 range)
  • [Ring Modulation] - enables the ring modulation affecting the instrument.
  • [Duty] - specifies the width of a pulse wave. (0-4095 range)
  • [Oscillator Sync] - enables the oscillator hard sync. As one oscillator finishes a cycle, it resets the period of another oscillator, forcing the latter to have the same base frequency. This can produce a harmonically rich sound, the timbre of which can be altered by varying the synced oscillator's frequency.
  • [Enable filter] - enables analogue filter affecting the instrument
  • [Initialize filter] - initializes the filter with the specified parameters:
  • [Cutoff] - defines the "intensity" of a filter, to put in in layman terms (0-2047 range)
  • [Resonance] - defines an additional controlled amplification of that cutoff frequency, creating a secondary peak forms and colors the original pitch. (0-15 range)
  • [Filter mode] - determined the filter mode NOTE: SID's filter is multi-mode, you can mix different modes together (like low and high-pass filters at once) CH3-OFF disables the channel 3, for no reason whatsoever lmao
  • [Volume Macro is Cutoff Macro] - turns a volume macro in a macros tab into a filter cutoff macro.
  • [Absolute Cutoff Macro] - changes the behaviour of a cutoff macro from the old-style, compatible to much more define-able.
  • [Absolute Duty Macro] - changes the behaviour of a duty cycle macro from the old-style, compatible to much more definable.
  • [Don't test/gate before new note] - Don't reset the envelope to zero when a new note starts. (Read "Test/Gate" below for more info.)

Macros

  • [Volume] - volume sequence (WARNING: Volume sequence is global for ALL three channels!!)
  • [Arpeggio] - pitch sequence
  • [Duty] - pulse duty cycle sequence
  • [Waveform] - select the waveform used by instrument
  • [Pitch] - fine pitch
  • [Filter mode] - select the filter mode/sequence
  • [Resonance] - filter resonance sequence
  • [Special] - ring and oscillator sync selector
  • [Test/Gate] - When on, the TEST bit resets and locks Oscillator 1 at zero until cleared. The GATE bit controls Oscillator 1's envelope: Gate on runs through the envelope's attack, delay, and sustain; Gate off is envelope release.