How do I get it to play in tune? - Yamaha P95 Digital Piano

To adjust the intonation on a guitar you need the following. ..
a electronic tuner
and a small philip screwdriver

when you tune a string say low E you play the note open and adjust tell it's in tune
then to intonate play the low E at the 12th fret
producing a Harmonic, view the tuner it will be sharp or flat,
turn the small philip screw on the bridge adjustment
it only takes a small turn one way or the other so go slow
once the string is tuned at the harmonic note check to see if it's in tune played open, keep tuning and adjusting tell the strings are in tune open and at the 12th fret on all six strings
once intonation is set properly the guitar will sound better
really hope that helps?

Good question, tuners can be simple and some are complicated
a basic automatic guitar tuner you would not have to do anything to the settings, just tune normal on the E string then slowly down tune to D most tuners are a little sensitive, so go slow
and one thing I always do is go lower than the note I'm tuning to then tune up tell it's correct, strings seem to stay in tune better
Hope this helps ?
and if you have time check back on my profile
I will be doing some video tips this weekend
showing tuning, and some basic guitar repairs
thanks for your time

buy a manual on Amazon or Ebay

Well friend,
According to page 24 of the manual here http://support.casio.com/pdf/008/ap_45_e.pdf
It says
Demo tunes
While holding down the MUSIC LIBRARY button,
press the PLAY/STOP button
.....and try to play a specific demo tune ........
After playback starts, press the tone button that
corresponds to the tune you want to play.from the list.

ALSO in the Troubleshooting section page 35 For DEMO tunes UNPLUG HEADPHONES

If it doesn't work, then you need to get a Technician to look at it.

This is an intonation issue. If you can find a music store that works with violins, talk to someone there who will certainly be better informed than I am. At least they can tell you if it's worth your time to fix it, or more cost effective to replace it.

Tell her to tune all strings below the pitch and always go up to the pitch, never down because of slack in the tuning keys. The gears will have a slight bit of play in them. If coming down and stopping at the right place, they will loosen and loose tuning when she lets go. Tuning from below and go up to the pitch will correct that. (more noticeable on electric) Also, I would take it to a shop to have the intonation checked and tuned if necessary.

Could be the level from your guitar is too high OR low. Too low the tuner can't get reliable signal... Too high and the tuner will see harmics of the strings. Make sure you set onboard shape or EQ's flat. You CANNOT tune while playing CHORDS... A single note at a time please...

Do NOT modify the guitar. Take it to a shop where they can set it up properly if you are having intonation or clearance problems. Also the quality of strings has a lot to do with changes in tuning. It is NOT uncommon for a guitar to require tuning during a half hour of playing. This is normal, especially if you are really driving it. Temperature affects the tuning drastically as well.

An autoharp makes chords by muting all the strings except those that make the chord. There would be 2 ways to change the chord structure. 1) retune the strings knowing which ones will be muted by each key so that the result is another but valid chord or 2) make your own "keys" so that they mute different strings.
The tuning of an autoharp is selected to allow you to play songs as long as they are in the right key or two. If you set it "like a piano" as you suggest, you could play those chords but not the chord sequences that make up most songs. Most songs revolve around sequences or intervals such as the popular 1 - 4 - 5 blues progressions. Most music has some predictable progressions and that's why the autoharp is tuned the way it is.
You can always experiment with different and odd tunings but if your goal is to play already written songs, I'd stick with the normal tunings - there are alternates.

That's the problem; you're using light gauge guitar strings. Chances are that if you are not used to playing strings that light, you're fretting hand will hit the strings with more force than is neccesary to fret them, thereby forcing them out of tune. You can solve this problem by adding more winds around the string post (three or more winds should do it), or you can switch to a heavier gauge of string.

If they're true locking tuners, they should have a notch on the back of the gear housing that you turn with a nickel to engage the locking mechanism once tuning has been established.

Also; check the intonation of the guitar itself on an electronic tuner. If it tunes right but sounds out of tune when played, this is an intonation issue, and can be solved by adjusting a small set screw that moves the individual saddle back and forth in the tune-o-matic style bridge. You can check this by tuning the string to the correct note, then playing the same string at the 12th fret and checking it against your tuner. If it rings in true, you're fine, if it comes up flat or sharp, every note on the fretboard is going to be off by that much, and you'll have to adjust accordingly (turn the screw to the right to add length and lower a sharp note, turn the screw to the left to subtract length and raise a flat note, if I remember right).

Hope that helps.