My two pence worth . . If you have ambitions to be a concert pianist and just play classical piano taking exams are essential. I you would like to study music at music college, then again you need have passed a grade 8 music exam and done some theory as well to get accepted.
Taking exams mean you have to learn lots of different scales which are really helpful and important to be able to play (properly)!
I took exams but found having to learn a piece I didn't like and having to play exactly what was written down on the score restrictive?
I really started to enjoy playing when i realised I could improvise, so I threw most of the books away and played by ear with the help of a few basic chords (Fake Books).
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I had piano lessons in the sixties. They cost five shillings (25p an hour). I went to a piano teachers house who lived nearby . . her name was Mrs Walton from Hoyland. She was very strict and had a ruler which she used to bang your knuckles with if you played something wrong! I was a good pupil so it didn't happen to me that often!
You had to pay for your music books which were quite expensive.
I never took any exams with her (can't remember why not). But the piano exams were the A.B.R.S.M (Associated Board of the Royal School of Music) exams, just like they are now, don't thing they've changed much in 50 years. I took some exams later on when I was in my thirties.
Hope this helps with the writing of your book.