Roland Aerophone mini AE-01

Four stars, because the instrument brings fun, is cool and easy to play. Although battery powered, it lasts for hours of playing (using ~2000mAh rechargable accumulators)

However, the quality of product itself is little bit lower - seems like a toy to be honest, lower than one would expect for the price. Especially keys make "toyish" sounds when pressed.

Sound it produces is nice, especially when played on external speakers. Apps on android - complete lack of documentation, non intuitive, zero grade.