Effect 4xy

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4xy is the vibrato effect. It can be used on any channel except DPCM. x sets the speed of the vibrato, with larger value meaning faster vibrato. 0 (40y) disables the vibrato. y = depth, larger value means deeper vibrato.

Note: 2A03 has a bug that resets the duty phase when switching between certain frequencies. This can be heard as a pop and might be noticable when using vibrato or pitch slides across those frequencies.

Vibrato Speed

A full vibrato cycle is 64 steps long, and the speed setting (x) defines how many steps to add at each engine tick (e.g. speed 1 requires 64 ticks to complete one full cycle, or 1.07s or 0.93Hz under the NTSC engine). Therefore, the frequency of a vibrato can be calculated as:

Frequency (Hz) = Engine * Speed / 64

or, expressed in BPM:

Frequency (BPM) = Engine * Speed * 15/16

For the NTSC and PAL engines, these calculate to:

Speed Period Frequency BPM
NTSC PAL NTSC PAL
1 64 0.93Hz 0.78Hz 56.25 46.88
2 32 1.88Hz 1.56Hz 112.50 93.75
3 21.3 2.81Hz 2.34Hz 168.75 140.63
4 16 3.75Hz 3.13Hz 225.00 187.50
5 12.8 4.69Hz 3.90Hz 281.25 234.38
6 10.7 5.63Hz 4.69Hz 337.50 281.25
7 9.1 6.56Hz 5.49Hz 393.75 328.12
8 8 7.50Hz 6.25Hz 450.00 375.00
9 7.1 8.44Hz 7.03Hz 506.25 421.88
10 6.4 9.38Hz 7.81Hz 562.50 468.75
11 5.8 10.31Hz 8.59Hz 618.75 515.63
12 5.3 11.25Hz 9.38Hz 675.00 562.50
13 4.9 12.19Hz 10.16Hz 731.25 609.38
14 4.6 13.13Hz 10.94Hz 787.50 656.25
15 4.3 14.06Hz 11.72Hz 843.75 703.13
16* 4.0 16.00Hz 12.50Hz 900.00 750.00

Note: A vibrato speed of 16 cannot actually be specified with the 4xy effect. It can, however, be created in the Instrument Editor using a pitch sequence of | 0 -y 0 y.

Vibrato Depth

Note: Depth is in frequency register units, the perceived depth will vary depending on the note pitch.

Ver. 0.3.0 to 0.3.5
Effect Depth
4x0 1
4x1 1
4x2 2
4x3 3
4x4 4
4x5 7
4x6 8
4x7 F
4x8 10
4x9 1F
4xA 20
4xB 3F
4xC 40
4xD 7F
4xE 80
4xF FF
Ver. 0.3.5 onwards
Effect Depth
4x0 1
4x1 3
4x2 5
4x3 7
4x4 9
4x5 D
4x6 13
4x7 17
4x8 1B
4x9 21
4xA 2B
4xB 3B
4xC 57
4xD 7F
4xE BF
4xF FF

Example

C-4 00 F ---
--- -- - ---
--- -- - 462
--- -- - ---
--- -- - ---
--- -- - 400

C-4 is note, 00 is instrument number, F is volume. Vibrato starts from line with 4xx effect and will continue until 400.

Notes

  • It is somewhat possible to influence the starting phase of a vibrato by using a 4x0 command to activate the vibrato engine at least one row prior to the normal 4xy command. This does, however, require careful timing.
  • Combining a 400 and 4xy command on the same row of a channel will reset the phase of the vibrato engine on that channel.


Effect list
0xy - arpeggio 1xx, 2xx - pitch slides 3xx - portamento 4xy - vibrato
7xy - tremolo Axy - volume slide Bxx - jump to frame Cxx - stop
Dxx - skip frame Exx - volume Fxx - speed and tempo Gxx - note delay
Hxy, Ixy - hardware sweep Hxx - FDS modulation depth Ixx, Jxx - FDS modulation speed Pxx - fine pitch
Qxy, Rxy - note slide Sxx - mute delay Vxx - duty/noise/wave mode Wxx - DPCM sample speed
Xxx - DPCM sample retrigger Yxx - DPCM sample offset Zxx - DPCM delta counter