Band Pass Filter

amp: 1 mix: 1 pre_amp: 1 centre: 100

with_fx :bpf do
  play 50
end

Combines low pass and high pass filters to only allow a ‘band’ of frequencies through. If the band is very narrow (a low res value like 0.0001) then the BPF will reduce the original sound, almost down to a single frequency (controlled by the centre argument).

With higher values for res we can simulate other filters e.g. telephone lines, by cutting off low and high frequencies.

Introduced in v2.3

Parameters

amp:

The amplitude of the sound. Typically a value between 0 and 1. Higher amplitudes may be used, but won’t make the sound louder, they will just reduce the quality of all the sounds currently being played (due to compression.)

Default: 1
Must be zero or greater
May be changed whilst playing
Has slide parameters to shape changes

mix:

The amount (percentage) of FX present in the resulting sound represented as a value between 0 and 1. For example, a mix of 0 means that only the original sound is heard, a mix of 1 means that only the FX is heard (typically the default) and a mix of 0.5 means that half the original and half of the FX is heard.

Default: 1
Must be a value between 0 and 1 inclusively
May be changed whilst playing
Has slide parameters to shape changes

pre_amp:

Amplification applied to the input signal immediately before it is passed to the FX.

Default: 1
Must be zero or greater
May be changed whilst playing
Has slide parameters to shape changes
Scaled with current BPM value

centre:

Centre frequency for the filter as a MIDI note.

Default: 100
Must be a value greater than or equal to 0
May be changed whilst playing
Has slide parameters to shape changes

Slide Parameters

Any parameter that is slidable has three additional parameters named _slide, _slide_curve, and _slide_shape. For example, 'amp' is slidable, so you can also set amp_slide, amp_slide_curve, and amp_slide_shape with the following effects:

_slide:

Amount of time (in beats) for the parameter value to change. A long parameter_slide value means that the parameter takes a long time to slide from the previous value to the new value. A parameter_slide of 0 means that the parameter instantly changes to the new value.

Default: 0

_slide_shape:

Shape of curve. 0: step, 1: linear, 3: sine, 4: welch, 5: custom (use *_slide_curve: opt e.g. amp_slide_curve:), 6: squared, 7: cubed.

Default: 5

_slide_curve:

Shape of the slide curve (only honoured if slide shape is 5). 0 means linear and positive and negative numbers curve the segment up and down respectively.

Default: 0