Hello. This is a question about sight-reading music.What is the trick to Reading..
The L/H  and R/H...together at the same time!How can your Mind..read
and understand "two" separate parts..at one time?Especially when you
have to play a piece "cold'.My question pertains to "Sight-reading"
only.Thank you.

Hello,
As mentioned on the second site below, lack of sight-reading skill is
probably the primary reason why intermediate students give up playing.
 How awfully and personally true!

I hope that you find these sites interesting:
http://www.serve.com/marbeth/teaching_sight_reading.html
http://www.music.sc.edu/ea/keyboard/PPF/1.2/1.2.PPFke.html
http://www.fergusblack.com/html/s_read.html
http://www.soundfeelings.com/free/music-reading.htm

This may also be helpful and encouraging.  It mentions learning to
play by ear, that is, being able to recognize - hear -  the interval
to the next note and play the right key.  This is what singers do with
their voice: see the interval and sing the note.
http://www.lofthouse.com/music/piano/duetime.html

Here is a more interesting idea:
http://www.juggling.org/jw/90/1/soprano.html

This is more conventional advice:
http://www.marycliff.co.uk/sitepage/sightreading.html
http://www.musicteachers.co.uk/resources/sightr.pdf

And there are also software aids, but I know nothing about them:
http://www.adventus.com/
http://www.educational-software-directory.net/music/piano.html

Take heart, it can be learned.

I'm no expert, but I do play a bit and am fairly decent at sight
reading. To me, the key is to practice exercises, you know, scales,
arpeggios, etudes, etc. Yeah I know, b-o-r-ing, and I also know
there's disagreement on the issue. But I think the reason it works is
that it helps to create a certain muscle memory in your fingers, that
will then take over whenever you encounter a certain pattern in the
written music. The more and greater variety of exercises you practice,
the greater the variety of patterns you'll be able to play on sight.
My two cents merely, but it seems to work for me.

Good luck,
Byrd-ga

When I was a kid, I was sure I couldn't sight read music.  Then an
uncle said, "Sight-reading is just a mental process--like reading a
book."  With this demystification of sight-reading--and a lot of
practice--I got pretty good at it.

It you keep practicing sight-reading--even each hand separately--your
mind will be able to "collect" the information faster than you need
it, even if you're reading two or more lines of music at a time.