I just bought a Yamaha PSR 400 and I figured out the first 8 keys? will play a style with
left hand while the remaining keys play an instrument sound called voice
sound.

I could do a song with the Piano set on style and using a rock ballad.
So I decided to try another song and using a Dixie and a different
style and it would not stay set.

I understand how to select voice.
But don't know how to keep it set when adding the rhythm style a jazz or
My husband figured out how to play split voices. He says the
style is for back up mucic it's a tune and it plays constantly if you
want it to.
But I thought I had the first 8 keys playing the style with right hand
only pressing one key at a time and holding it for 4 beats and playing
the voice section with the right hand .
I know my husband is correct but am I completely wrong. I have not been
able to figure out how to play the style and voice again and the easy
music I have shows a key in a box like an F above the other keys to play
with the left hand on far left of key board and the other keys a voice
and tune on right of board.
Can you throw some light on this for me. Ask me another question
regarding this if you need to understand my question. Jeanie

Jeannie,
Glad to have you aboard. Those of us that have played arranger keyboards for years often take too much for granted. They can be intimidating at first.
The first thing you should do is set down at your keyboard with the owner's manual. Go through each step in the manual. If you don't have one, you can download one from the Yamaha web page at no cost.
You'll find that there are several modes in which the keyboard can be set, one of which, sure enough, lets you play either single-finger or multi-finger chords on the first 8 notes on the left. The point at which the melody notes start playing is called the Split Point, and it can be adjusted to suit your taste.
All this is explained in the manual, and I believe it is essential for you to read it before you can proceed much further.
Then we'll be happy to help you all we can.
Good luck and welcome to the world of arranger keyboards.
DonM

Jeannie,
It sounds to me like you have turned on a feature on all Yamaha keyboards called "one touch settings". If you have this button turned on (and you should see it in the display), everytime you change styles the right hand sound will change along with the style you have picked. If you turn of the OTS button, then you can change a style and the right hand sound will stay on whatever sound you are using.
Try this and look in your owners manual under one touch settings.
George Kaye
Kaye's Music Scene