The greatest advantage of the accordion is that like a piano you can play different parts with the left hand and right hand making it possible to play both lead and rhythm. This makes a lone accordion very pleasurable to listen to compared to a trumpet or a guitar since you can play both the bass, rhythm and lead part of a song by yourself. The accordion also works great in a band setting since its portable compared to a piano.
Compared to a piano there is also another great feature. To play chords on a piano you have to remember certain combinations of keys you play with your left hand. Since there are lots of chords in lots of keys this is a very hard task. On the accordion however this is solved with the incredibly smart
Stradella system that enables you to play almost any chord with a single button push.
