Methods, systems, and devices are described for automatically converting audio input signal data into musical score representation data. A crank arm section connecting the crank pin section and the crank journal section is formed with each of lateral edge portions extending substantially along a circumscribed tangential line connecting a base of the crank pin section and a base of the crank journal section when viewed in the direction of the crankshaft. The multistage amplifier includes two or more transistor stages connected together in a global feedback arrangement. The second door panel has a top section proximate the bottom section of the first door panel. Consequently, the battery module is easily fabricated, and the occurrence of short circuits is effectively prevented during the assembly or the operation of the battery module.