Yamaha PSR-S650 Reference Manual - Page 13

Harmony/Effect-Related Settings Voice Sound and Effect Type You can select one type from each effect (Reverb, Chorus and DSP) then individually adjust the amount of effect that is applied to the Main, Dual, and Left Voices. However, the effect type cannot be applied independently to each Main, Dual or Left Voice. Because of this, you should adjust the send level for each Voice when using effects. When the DSP function is on, the overall sound may be wrong or unexpected if the Main Voice is changed. This is because the DSP type is automatically selected according to the currently selected Main Voice and the same effect is applied to the Dual Voice or Left Voice as well as the Main Voice. If you want to enhance the sound using the DSP, determine the Main Voice first, then adjust the send level of the DSP effect applied to each Voice. The Reverb/Chorus type is automatically selected according to the currently selected Style or Song, and the same effect is applied to the Dual Voice or Left Voice as well as the Main Voice. If you want to create a custom sound using a favorite Voice, determine the Voices, effects and Voice parameters first, then memorize the settings to the Registration Memory without changing the Style or Song. Reference Manual 13