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59 lines
2.5 KiB
Markdown
59 lines
2.5 KiB
Markdown
# 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
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- `01`: triangle
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- `02`: saw
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- `03`: triangle and saw
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- `04`: pulse
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- `05`: pulse and triangle
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- `06`: pulse and saw
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- `07`: pulse and triangle and saw
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- `08`: noise
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- `11xx`: **set coarse cutoff.** `xx` may be a value between `00` and `64`.
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- _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`.
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- _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`.
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- `14xx`: **set filter mode.** the following values are accepted:
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- `00`: filter off
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- `01`: low pass
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- `02`: band pass
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- `03`: low+band pass
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- `04`: high pass
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- `05`: band reject/stop/notch
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- `06`: high+band pass
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- `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.
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- 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.**
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- `1Bxy`: **reset cutoff**:
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- if `x` is not 0: on new note
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- if `y` is not 0: now
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- 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
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- if `y` is not 0: now
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- 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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- `x` may be one of the following:
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- `0`: attack (`y` from `0` to `F`)
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- `1`: decay (`y` from `0` to `F`)
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- `2`: sustain (`y` from `0` to `F`)
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- `3`: release (`y` from `0` to `F`)
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- `4`: ring modulation (`y` is `0` or `1`)
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- `5`: oscillator sync (`y` is `0` or `1`)
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- `6`: disable channel 3 (`y` is `0` or `1`)
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- `3xxx`: **set duty cycle.** `xxx` range is `000` to `FFF`.
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- `4xxx`: **set cutoff.** `xxx` range is `000` to `7FF`.
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