i remember some more.
The first character is some kind of composer/musician on a boat by himself to rest, relax and make music.
The 'good' aliens end up landing near him and making contact with him. This occurs at night, the guy is woken up by an alien, and despite him being a fairly 'normal' civilian he breaks the aliens arm and flees the ship, impressing upon the aliens his strength, speed, swimming ability etc.
It all gets straightened out with the aliens trying to convince him humans would be of great help in the fight, and their cause is just etc.
Anyway the story moves on from there. I think there are a few books.
Last thing i remember, the chief evil race has some sort of telepathic ability, but when they use it on a human, they get this massive, violent emotion backlash which usually kills the alien.
anyway, anything that sounds like it could be it.