I don’t think it is a particularly common to think about what instrument suits what personality, but I believe some scientists somewhere have done a study to try and match personality types to musical instruments. I once knew a high school music teacher that channeled students into playing certain instruments solely on what he believed there personality was like. For instance, it was recommended that people who have big, outgoing personalities, should choose a brass instrument – kind of adds a new meaning to the saying ‘bold as brass’.
If you are interested in learning to play a musical instrument, then this could be a useful tool in helping you decide, but if you have your heart set on playing the piano or any other instrument for that matter, then that is what you should proceed to learn.
As the piano has such a diverse repetiore and it can be used in a variety of settings such as soloist, duet with two people playing on the same piano, multiple pianos and performers performing together. Piano players can perform the role of accompanist to a singer or other instrument soloist, as well as part of a band or ensemble of varying sizes. A piano player can perform solo and be the centre of attention to being part of a band or ensemble where they add to the overall sound and can just almost blend into the background, so playing the piano can suit pretty much any personality type.
When it comes to talking about what instrument suits what personality types, it is not just about what suits which instrument when it comes to performing but what personality is best suited to what type of practicing. Piano players do the vast majority of their practicing by themselves, whereas other instrumentalists would need to practice more in a group than individually. This last point I have only fully realized since two of my kids play band instruments – one plays the trumpet and the other, a saxophone. I have rarely heard them practice at home but they have often talked about practicing with their friends and the information I have always gotten from their instrument teaches has been that they were always progressing well. I realized that because their music that they have had to learn has always been a part rather than the whole piece of music, it makes sense that their preference would usually be communal practicing.
This is one reason I argue that the playing the piano suits an introvert, is because you can play music is complete without adding other instrument parts. An introvert can choose to only ever play music by themselves and therefore only ever need to practice by themselves.
An introvert could also learn to play the piano without anyone outside of their household ever knowing. This is possible, in part, due to the fact that you can easily buy an electric piano and only ever play it with the headphones plugged in. Other musicians playing other instruments, can’t quite achieve the same thing.
So while I haven’t made a long list of reasons why, I think it is quite clear that through the use of an electric piano, learning the piano more than any other instrument, would suit an introvert.