Read these books when I was a youth and loved them. I haven't been able to remember what they were at all for years.
The details I do remember are this:
They had talking Otters who raised the main character (a young boy).
The dragons were lost or nearly extinct and the young boy had to bring them back.
In order to do their magic they had to sing or play music.
Every search I do on Google for these criteria just get me the books by Christopher Paolini about Dragons and those are not what I want.