It is recommended to read How WIDI works first before adjusting the Equalizer.

To call Equalizer, use "Options->Show Equalizer" menu item or the Equalizer  button on the toolbar. You can also use the diminished picture of the Equalizer in the right-bottom corner of main WIDI window. Click on to bring up the Equalizer.

WIDI Equalizer has very little relation to the "Equalizer" in its conventional meaning.

The purpose of Equalizer is to let you select or enhance note recognition possibility for different pitch ranges. It consists of a bar chart and a fingerboard underneath it. By pressing the left mouse button anywhere in the chart area you can adjust the corresponding note volume or possibility to detect such a note.

Let's imagine we have two simultaneous notes with equal volumes, say C-1 and D-6. Your may consider first note to be a correctly detected bass note, and the second one to be an erroneously detected overtone of some lower note. WIDI algorithm picks no more than several (determined from "Maximal Polyphony" parameter) loudest notes at a moment and rejects all others. So if you stress C-1 and diminish D-6 with Equalizer you may force WIDI not only to diminish D-6 note volume but also to reject it at all.

On the following screenshot, all pitch volumes are set to 50%, except C-1 is set to maximum and D-6 is set to 10%.

Equalizer consists of two tabs – Pitch and Scale Mask. Resulting multiplier coefficient is determined as a product of corresponding Pitch and Scale Mask values and is shown with darker blue.

Pitch tab allows to suppress or stress specific absolute pitch ranges or particular pitches.

Scale Mask controls how different scale degrees are treated. For example, you may need to remove all third degree notes in C Major key. The following picture shows how to set up Scale Mask for this task:

Next screenshot demonstrates  how pitch mask looks after this modification. You see that changing only one degree affects 7 different pitches, all of them being the third degree of the selected scale.

Pitch mask is recalculated immediately after scale mask is updated, except when the Use recognized key box is checked. In this case correct key will be set only after tonality analysis during recognition process. If you do not know the key of the musical piece, you can use this option.

Note: Use recognized key checkbox does not control whether the tonality analysis will be actually performed. If no tonality is detected automatically, Use recognized key control does not take any effect. To turn on tonality analysis, use a checkbox in the MIDI Options tab of Recognition Settings dialog. Note that setting Use recognized key and turning on tonality analysis will force WIDI to perform recognition twice - first time to determine the tonality and then second time to produce actual notes. See How WIDI Works for more comprehensive description.

It may be very convenient to use Scale Mask to reject some degrees that are out of scale, this may increase transcription accuracy significantly. If you do not need to use the feature, just create a flat Scale Mask (you can do this by double-clicking Chromatic item).

This screenshot shows typical Equalizer settings for the Natural C Major piano performance:

In this example all notes that are not degrees of Natural C Major key are suppressed, typical pitch range of melodic voice is emphasized, and lowest and highest pitches are cut out to zero.

Equalizer settings may be saved to a file with a .weqp extension using the Saving Settings function.