Simple Piano is a free Android app developed by retlat in the Multimedia category, specifically for music and radio. It is a 1 octave keyboard app that allows you to play up to 5 keys simultaneously, depending on your device's specifications.

One of the notable features of Simple Piano is that it supports multi-window on Android 7.0 (Nougat) and later, which allows you to use other apps while playing the piano. Additionally, users can take advantage of the app's dark theme feature on Android 10 and later.

Overall, Simple Piano is a straightforward and simple app that is perfect for casual use and beginners. The app's minimalist design and functionality make it easy to use and understand, but it may lack the advanced features that more experienced users may be looking for.