Some teachers use them and some don't. I've heard that they can become a crutch and cause delayed ear training development, but others say they are necessary at the beginning. Can they really cause ...
I heard that it becomes very difficult to learn to play violin after a certain age (14 IIRC). Is that correct? And what is the reason?
As the title asks, I wish it could be clear to me. Can someone give me a good characterization? Do you produce them differently on a cello than on a violin or viola?