Playing two notes with one finger

[robfigee]

Hi everybody. On my old Casio I had a button called autohamonize, when activated I could play an E and the keyboard played E and C. With the F it played F and D making a fifth. This worked when using left hand chords with a style playing.
I am sure the PSR 770 can do this too, but could not find out how.
If so, I would gladly hear how I can do it.
Thanks in advance,

Rob

[SciNote]

On my PSR-E433, there is a function called "Harmony" which does something very similar to what you describe.  I'm pretty sure the S770 has something similar.  I know on my E433, there are a variety of harmony options, such as duet, trio, and country which determine what notes will be played along with your melody note, so you need to try different setting options to see which one does what you want.  On my E433, this function only works with auto-accompaniment style chords turned on, and of course, the notes played along with the melody note are dependent on the left hand auto-accompaniment chord you are playing.  The S770 may have more options.