Filter Types

Filter Window

These controls are identical across all engines and also available in the DynFilter effect.

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The Formant Filter

Formant Window

When the formant window is selected, the FilterType list is replaced by an Edit button, and clicking on this opens the window shown. These controls are additional to the others and adjust individual formants and the vowels they are contained in. Also, remember that the formant filter interacts with the filter envelope.

There are six vowels each with 12 formants, although you can chose to use only 2 or 3 of these.

For a deep understanding of formant filtering there is a highly detailed Wikipedia article Here.

Note
Although the sequence size sets the number of active vowels it doesn't determine which ones can be selected for any sequence position. If you have three vowels active (the default) you could have vowels 6, 3, 4 at positions 1, 2, 3 respectively.

The Formant Graph

You can control some of the parameters by placing the mouse pointer over the yellow lines representing each formant. While making changes, the respective controls will move accordingly.

Holding down either left or right mouse buttons and moving the mouse sideways will change the formant's center frequency.

Moving vertically while holding down the left button will change the amplitude. Alternatively holding down the right button changes the formant's Q factor.

Anywhere on the graph, the scroll-wheel changes the octave range, and holding Shift at the same time changes the center frequency.

If your mouse has extra buttons on the sides (many haven't) these can be used to switch between the formants instead of moving the mouse across to the next one.

This is especially useful for controlling most of the formant features one-handed, quickly, while also playing on a keyboard.

The Formant Pseudo Default

When a formant filter is first created the frequency control for each of the individual formants will be set randomly. However, with Yoshimi versions V2.3.0 and later, this setting becomes a pseudo default and the knob pointer colour will behave accordingly.
An extra wrinkle is that if this has been changed and the instrument is then saved, the saved copy will have the current value marked as the default, without affecting the running version.
Also, keep in mind that a reset, or switching to a different filter type always clears all filter settings and the formant frequency controls will gain new random values.