I play it for a hobby and I read some music theory books. I mainly only cover songs.
But I enjoy it as well.
You can check out my youtube channel for some of my videos : *www.youtube.com/user/dessavio/videos
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If you want details of what I know, I know a couple of chords, I practice the Pentatonic, Minor and Harmonic Minor scales and impro on them and tapping arpeggios, etc.
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Yeah I did mention that it was not necessary. Thanks for the information though. Even I'm thinking of starting(actually I do know a little since I live in a hostel and many of my friends already know how to play the guitar).
You should take the time to learn from your friends.
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It is mainly used to set a song in a higher key. For example a song in the key of E would become a song in the key of F# if you put the capo on the 2nd fret, while maintaining the pattern of the chords from the key of E.
But you can transpose chords anyway without a capo, only the pattern changes.