It's confusing, but I think pronouncing it 'base' is generally accepted.
II'm not sure about treble. I've heard 'treb-el' and 'tree-bol' and am not so sure which is right
It's the first pronunciation. "treh - bul".
I am so lucky to be a native English speaker, if I had to learn this shit as a second language I'm pretty sure I would just give up. Spanish was easy to learn in comparison.