Before 1730, clavichords were created small with four octaves and a length of approximately four feet but nowadays, these are made with a length of up to seven feet. Nowadays, clavichords are manufactured all over the world and have many buyers in the market. A few modern manufacturers are the British Peter Bavington, Swiss Thomas Steiner, American Charles Wolff, and Belgian Joris Potvlieghe. The body is made of two wooden boxes joint by bellows. In these are the reed chambers which produce sound. The pallets are valves that control air passing through to the reeds. The pressing on the key raises the pallet which allows air to enter the reed chamber and air flow stops as the key is released. Acoustic Guitar The acoustic guitar is hollow-bodied and uses only acoustic techniques to produce sound which means it does not have electric amplification. Its name is a retronym of the electric guitar to differentiate them from each other. Its strings could be made of steel or nylon while its top plate could be made of cedar or spruce. To have a smoother edge, the mouthpiece could also be lined with beeswax. Shapes of didgeridoos Didgeridoos do not have a standard or uniform size or shape. The tube s length and its almost conical shape affect the acoustic performance of every individual instrument. The didgeridoos that are in demand are those measuring from 1 meter to 1.6 meters. Most are made of bamboo and high-pitched. Fue have two varieties. One is the end-blown flute which has a hole on both ends. The other is the transverse flute which is held horizontally with the embouchure hole only near one end. How does the flute work? A rapid jet of air blown by the flute player from the mouthpiece is the source of power for playing the instrument. In 1953, the Gibson Guitar Corporation put the electric bass with a violin shape and an expandable end pin on market. These had one humbucker right alongside the neck pocket. Rickenbacker released the model 4000 bass which had a neck-through-body design in 1957. High end bass guitars which have unique designs, onboard electronics, and hand-finished bodies rose in the 1970 s.