How to tune your guitar by using a keyboard or a piano. Start out with low E on the piano. Make sure you have LOW E. Play Low E on the piano and then play the 6th string open on your guitar. Now, just tighten or loosen the 6th string of your guitar to match the Low E on the piano. For the next key just count up 4 keys including Low E. So, you would count EFGA….1-2-3-4…..Now you can tune the 5th string or the A string of your guitar. Next, count up 4 white keys from A……ABCD…..1-2-3-4. Now you can tune the 4th string of your guitar which is the D string. Do the same thing as you did before. Count up 4 white keys from D…starting with D……DEFG….1-2-3-4….Now you can tune the 3rd string of your guitar which is G to the G key on your keyboard. Here is where the RULE changes. At this point, count up ONLY 3 white keys starting with the G……GAB…..1-2-3. Now match the 2nd string B to the keyboard B. Here is the last step. Go back to your rule of counting 4 keys. Start with B and count 4 keys up: BCDE….1-2-3-4. Now just repeat the same process and match up the open 1st string E on your guitar with the E on the keyboard. Be very careful at this point. To not tighten your E string to tight. Pay attention. You could easily over tighten the 1st string and it will snap in half. Ive done it many, many times over the last 40 years.