What am I describing?

Chapter 1

I am pretty large. On the front of me, there is a row of small, strange-looking rectangular prisms. If you push down on a prism, an object inside me strikes another object. I let out a sound.
I can make more than eighty different sounds.
I don't have moods or feelings, but sometimes, if I make a lot of sounds together, I might be able to cause you to feel happy or sad.
Sometimes, someone teaches someone else how to be near me and how to make my sounds ring out.

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I'm kind of like you. I love making noises, eating, and playing. I'm also smart. Some people think I'm ugly.
There are different types of me. One type is really loud and you can hear it from far away. Another type is extremely strong. There's a kind that is very similar to you.
One person - a GOOD person - spent some time with us.