You've probably run your finger around the edge of a crystal wine glass, creating a haunting musical note. You also might have noticed that if others were doing the same with their wine and water glasses, different pitches were dependent on how much water or wine was left in the glass. You also might have noticed that larger glasses produced lower tones and smaller glasses produced higher tones. This is the principal for the glass harp, sometimes referred to as the glass harmonica, invented by Benjamin Franklin. You can easily create an instrument with the same effect.
Wet your finger and run it around the rim of your largest glass until you produce a sound. This may take some practice. Find the note that is closest on your tuning instrument to the note produced on the glass but a little bit lower. Put some water in the glass and check the pitch again. If the note is still too high, add more water, but if you've gone below the pitch of your tuning instrument, pour some of the water out until you match the pitch perfectly.
Set this glass near the middle of the tray and near the left edge.
Take another glass that is the same size as your first glass and add water until it is at the same height as your first glass; test your pitch. It should be the same as the first glass, but because of variances in manufacturing, it may be different.
Adjust the amount of water by deleting a small amount so that the note in the second glass is one-half step higher than the note in your first glass. After you have matched pitches with your tuning instrument, place the second glass to the right of the first glass and in a new row above the first glass.
Repeat steps 2 and 3 for the first five glasses. This will give you the first five notes of a chromatic scale.
Fill the next glass with enough water to match the pitch of the fifth glass and adjust the pitch as before. Place this glass next to the fifth glass and continue filling glasses and raising the pitch by one-half step until you have 12 glasses, thus making a complete chromatic scale. As you progress up the scale, you will probably have to change to smaller glasses in order to obtain higher notes.
Continue building your glass harp until you have your desired range. Some really proficient players will utilize up to 48 glasses (four octaves).
You must use glasses with stems to make this work, and better crystal works more effectively that cheaper glassware. After you have your glasses arranged like a piano keyboard, you may want to move them around in a manner that is more comfortable for your use.
Make sure your surface is solid, because movement could cause the glasses to fall over. Your fingers must be clean and free from body oil for them to produce a tone on the rim of the glasses.