Use EQUA button on the top of the main window to bring up the Equalizer window.
Equalizer allows to enhance or decrease selected pitch ranges or even particular notes. Note volume is multiplied on the corresponding equalizer value before a acceptance decision for the note is taken. By pressing the left mouse button anywhere in the chart area you can adjust a particular note value. In the following example all notes in the middle range are more likely to be recognized.
The buttons 0%, 50% and 100% put all bars of the Equalizer to the corresponding positions.
Note: Because only relative probability values are set, there is no difference between 100% and 50% positions. Use them as an intermediate step of equalizer adjustment.