Xylophone’s a wonderful instrument. It has a rich history, dating from the 9th century and being developed independently in both Africa and Asia. It enjoys widespread use in everything from traditional African tribal music to an American elementary school classroom, where it is used to teach introductory music principles to children. While building a full-scale modern concert xylophone would represent a massive undertaking, it is relatively quick and easy to make a one-octave, diatonic xylophone.
Cut the keys roughly to size. A good approximation is to cut the lowest note to about 14 inches (35 cm) long and the highest note to about 10 inches (25 cm) long. The keys in between should gradually bridge the gap between these 2 lengths. With these lengths, the keys can be tuned easily to the C Major scale. The exact length of each key is not important, as you will be trimming them down during the tuning process.
Find the position of the nodes on each bar. The nodes are the parts of the bar which will not vibrate when the bar resonates, and are located about 2/9 of the length of the bar in on each side. To find their exact position, sprinkle salt on each key and strike it repeatedly with a mallet. The salt will dance around on the bar and gather on the nodes (because there is no vibration there). Mark this position with a pencil.
Lay the keys across these 2 pieces of wood with the nodes of each key positioned directly over the frame. Drive nails through the pre-drilled holes in the keys and into the wood frame below. Attach the 2 long pieces of wood to each other to keep the frame rigid. Take the other 2 pieces of wood reserved for the frame and screw, nail or glue them across the 2 long pieces to form a 4-sided frame.