A music stand is a pedestal or elevated rack designed to hold a paper score or sheets of music in position for reading. Most music stands for orchestral, chamber music or solo orchestra-family instruments (violin, oboe, trumpet, etc.) can be raised or lowered to accommodate seated or standing performers, or performers of different heights. Many types of keyboard instruments have a built-in or removable music rack or stand where sheet music can be placed. Music stands enable musicians to read sheet music or scores while playing an instrument or conducting, as the stand leaves the hands free. Music stands are sometimes used by singers, however for choirs, singers typically hold their sheet music in a folder, and singers performing solo recitals or opera performances typically memorize the lyrics and melodies. Some singers use stands, such as lounge singers and wedding vocalists who have a repertoire of hundreds of songs, which makes remembering all of the verses difficult.