“The importance of learning to play music

-- As you want to include everyone, you should use "and". The word "or" is more exclusive. This or that, but not both.

For example, you can start to play an instrument with your best friend when you are a child or you can choose to learn to play music in your adulthood with the aim to join to the local band of your town.
In fact, several scientific research has demonstrated that music makes you happier and more energetic. At the same time it improves your concentration and enhances your sense of responsibility.

-- Scientific researches is not said. If you want to talk about specific research by multiple people, you would call it scientific studies.

-- It [...] enhances. Even if the verb is far away from the subject, you must still connect them.

Secondly it has been proven that if a person learns to play an instrument during its primary school, he or she becomes a more intelligent and creative person. For this reason there are some mothers that listen music while they are pregnant because they thinks their baby can listen to it too.

-- Never use "it" to talk about a person. It is very rude.

Finally we should be reminded of the proverb “passion is the salt of your life”. So I think it's important to remember that if you would like to play music, it's not relevant if you choose to play classical, rock or pop music, the essential thing is that you play with passion. Let your heart express itself.

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Have a nice day!