Effect commands

What are effect commands

A pattern table is composed of cells telling the tracker which notes to play in which order. It also has a field for effect commands. It is often represented as a three digit hexadecimal value. The first hex digit represents the effect command, the latter represent parameter values used by the command. The table below (based on data(effect_commands)) summarises all available effects in ProTracker.

More details on the tracker pattern structure can be found in vignette("s3class"). Some examples of the effects that can be applied are provided below. Note that this vignette does not intend to be a complete tutorial. It merely addresses how you can manipulate ProTracker modules programmatically in R. For more in depth information please check the references.

Extracting and updating effect commands

To get an effect command from a ProTracker module, you can simply call pt2_command() to a pt2cell or pt2celllist class object (see vignette("s3class") for a ProTrackR2 object tree). There, are several ways of extracting cells as documented in vignette("sel_assign"). In the example below there is one way shown of getting the effect commands of the first 8 rows of the second column in the third pattern.

## load the demo-mod included with the package
mod <- pt2_read_mod(pt2_demo())

pt2_command(
  mod$patterns[[ 3 ]] [ 1:8, 2 ])
#> C40
#> C30
#> 000
#> 000
#> 000
#> 000
#> 000
#> 000

You can also assign new effect commands to your selection like this:

pt2_command(
  mod$patterns[[ 3 ]] [ 1:8, 2 ]) <- "C10"

Examples of some common effects

Using the description in the table above, and the assignment procedure explained above, some examples are implemented below:

## create a new mod te demonstrate commands
mod_command <- pt2_new_mod("commands")
## copy the samples from the mod above
mod_command$samples <- mod$samples

if (interactive()) {
  mod_command$patterns[[1]][1,1] <- "C-3 01 000"
  ## Reduce sample volume
  pt2_command(mod_command$patterns[[1]][,1]) <- "C10"
  play(mod_command)
  
  mod_command$patterns[[1]][1,1] <- "C-3 03 000"
  ## Simulate major chord:
  pt2_command(mod_command$patterns[[1]][,1]) <- "047"
  play(mod_command)
  
  ## Simulate minor chord
  pt2_command(mod_command$patterns[[1]][,1]) <- "037"
  play(mod_command)

  ## Porta up:
  pt2_command(mod_command$patterns[[1]][,1]) <- "101"
  play(mod_command)

  ## Porta down:
  pt2_command(mod_command$patterns[[1]][,1]) <- "201"
  play(mod_command)
  
  ## Porta to note:
  mod_command$patterns[[1]][1,1] <- "C-3 03 000"
  mod_command$patterns[[1]][2:64,1] <- "E-3 03 000"
  pt2_command(mod_command$patterns[[1]][2:64,1]) <- "301"
  play(mod_command)
  
  mod_command$patterns[[1]] <- pt2_new_pattern() # reset pattern
  mod_command$patterns[[1]][1,1] <- "C-3 03 000"
  ## Vibrato:
  pt2_command(mod_command$patterns[[1]][,1]) <- "464"
  play(mod_command)
  
  ## Tremolo:
  pt2_command(mod_command$patterns[[1]][,1]) <- "743"
  play(mod_command)

  ## Fade out:
  pt2_command(mod_command$patterns[[1]][,1]) <- "A01"
  play(mod_command)

  mod_command$patterns[[1]][1,1] <- "C-3 03 C00"
  ## Fade in:
  pt2_command(mod_command$patterns[[1]][2:63,1]) <- "A10"
  play(mod_command)
}

Effect of instrument number on effects

The cells in a ProTracker pattern also hold information on the instrument number. The function pt2_instrument() can be used to get or set an instrument number. The reason for mentioning it here is that setting (or omitting) the instrument number can affect how a pt2_command() is interpreted.

By setting the instrument number in combination with an effect command, can cause the player to reset the sample’s previous state. I’m not going to show all features as there are many. But just as an example see what happens when you apply a volume slide in combination with setting the instrument number. The volume is reset each row of the pattern:

mod$patterns[[1]] <- pt2_new_pattern()
mod$patterns[[1]][1,1] <- "C-3 03 000"
## Slide the volume down in the entire track:
pt2_command(mod$patterns[[1]][,1]) <- "A08"
## Reset the volume each row by setting the sample
## number for the entire track
pt2_instrument(mod$patterns[[1]][,1]) <- 3L
if (interactive()) {
  play(mod)
}

References

• YouTube tutorial
• OpenMPT documentation on effects