Lukitoh,
The manual bass is never going to work well with a Yamaha harmonizer because it only recognizes vocoder style note triggers. This means that you have to assign the harmonies to thr RIGHT hand and hold down the notes for the ENTIRE duration of the sung harmony notes. Impossible in most situations.
The harmonizers in the psr2xxx and PAx0 both are linked to arranger functions, and work poorly when the arranger is off.
The Ketron works the best in this way, as does the outboard gear like Digitech and TC Electronics.