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# Commodore 64
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a home computer with a synthesizer-grade sound chip of which people took decades to master. three oscillators with four selectable waveforms, ring modulation, oscillator sync, multi-mode filter and ADSR envelope.
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very popular in Europe and mostly due to the demoscene, which stretched the machine's limbs to no end.
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two versions of aforementioned chip exist - 6581 (original chip) and 8580 (improved version with working waveform mixing and somewhat more consistent filter curves).
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## effects
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- `10xx` : **change wave.** the following values are accepted:
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- `00` : nothing
- `01` : triangle
- `02` : saw
- `03` : triangle and saw
- `04` : pulse
- `05` : pulse and triangle
- `06` : pulse and saw
- `07` : pulse and triangle and saw
- `08` : noise
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- `11xx` : **set coarse cutoff.** `xx` may be a value between `00` and `64` .
- _this effect only exists for compatibility reasons, and its use is discouraged._
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- use effect `4xxx` instead.
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- `12xx` : **set coarse duty cycle.** `xx` may be a value between `00` and `64` .
- _this effect only exists for compatibility reasons, and its use is discouraged._
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- use effect `3xxx` instead.
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- `13xx` : **set resonance.** `xx` may be a value between `00` and `0F` .
- `14xx` : **set filter mode.** the following values are accepted:
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- `00` : filter off
- `01` : low pass
- `02` : band pass
- `03` : low+band pass
- `04` : high pass
- `05` : band reject/stop/notch
- `06` : high+band pass
- `07` : all pass
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- `15xx` : **set envelope reset time.**
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- this is the amount of ticks the channel turns off before a note occurs in order to reset the envelope safely.
- if `xx` is 0 or higher than the song speed, the envelope will not reset.
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- `1Axx` : **disable envelope reset for this channel.**
- `1Bxy` : **reset cutoff** :
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- if `x` is not 0: on new note
- if `y` is not 0: now
- this effect is not necessary if the instrument's cutoff macro is absolute.
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- `1Cxy` : **reset duty cycle** :
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- if `x` is not 0: on new note
- if `y` is not 0: now
- this effect is not necessary if the instrument's duty macro is absolute.
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- `1Exy` : **change additional parameters.**
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- _this effect only exists for compatibility reasons, and its use is discouraged._
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- `x` may be one of the following:
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- `0` : attack (`y` from `0` to `F` )
- `1` : decay (`y` from `0` to `F` )
- `2` : sustain (`y` from `0` to `F` )
- `3` : release (`y` from `0` to `F` )
- `4` : ring modulation (`y` is `0` or `1` )
- `5` : oscillator sync (`y` is `0` or `1` )
- `6` : disable channel 3 (`y` is `0` or `1` )
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- `20xy` : **set attack/decay.**
- `x` is the attack.
- `y` is the decay.
- `21xy` : **set sustain/release.**
- `x` is the sustain.
- `y` is the release.
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- `3xxx` : **set duty cycle.** `xxx` range is `000` to `FFF` .
- `4xxx` : **set cutoff.** `xxx` range is `000` to `7FF` .
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## info
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this chip uses the [C64 ](../4-instrument/c64.md ) instrument editor.
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## channel status
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the following icons are displayed when channel status is enabled in the pattern view:
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- channel is silent:
-  it's not
-  gate bit disabled
-  gate bit disabled and test bit enabled
-  test bit enabled
-  ch3off enabled in filter mode
