From the owner’s manual: “The CS01 [Micro-Monophonic Synthesizer] incorporates advanced synthesizer technology and featured developed for the renowned Yamaha CS-series synthesizers with the added convenience and versatility of a lightweight, exceptionally compact format. Further, the CS01 has a built-in amp and speaker, and can be run on either batteries or an optional AC adaptor unit. The CS01 imposes no limitations on where or when you play. Outdoors, at home or on stage, the Yamaha CS01 gives you great Yamaha synthesizer sound and versatility.”