The Oktoberfest Instrument crossword solutions are the ACCORDION (9 letters) and the TUBA (4 letters). The ACCORDION is a type of free-reed aerophone instrument, which is made up of a keyboard and bellows. It is commonly used in folk music and jazz, and is popular in many countries around the world. The TUBA is a large brass instrument, usually with a conical bore and three to six valves. It is the lowest-pitched instrument in the brass family, and is often used in orchestras, marching bands, and other ensembles. Both the ACCORDION and the TUBA are popular instruments at Oktoberfest celebrations.