Question, what makes you feel that you can judge the jingle?
My background is advertising so I have written and helped create lots of jingle, in fact I worked with the guy who created the sound imaging that is all the station jingles and one liners including composing the music and writting the lyrics you hear on a couple of radio stations- Umhlobo, Ukhozi, and so forth.
Let's go back to my first question- music especially for ads and jingles is very subjective, the partenr created a jazz song because he probably likes jazz, you most likely hate it because you like hip hop.
That's why you came to a hip hop board. When you're subjective it's the work, in this case the jingle that suffers.
I think you'll have a better chance at fixing the current jingle with partner, by simple writting a catchier lyrics, shorten the jingle adding a horn section. If he created a jazz song- and you go come with a hip hop song you guys will never agree and again it will be the jingle that suffers.
Cool, let's say the jingle definately does not work- if this guy has any musical talent you guys are half way there. Now what you have to do is research the style, what musical genre is more suited for an enviromental company, acid jazz, that Enya slow shit, you guys agree on that.
Then pick up as many references of other jingles and even songs.
If there are lyrics to be written lock yourself in a room and just have fun.
Then between the two of you and who ever you both agree you need help from create the jingle.
Besides from writting, which is a cursed painfull solitary experience, creativity is all about colloborations, you have to open up and check the egos at the door and work.
The real art is how to persuade him to see things your way- that is something no one can advise you on.
It depends on the relationship and how you relate to people.
I'm no musician but I can help and for free. Send me the brief and the song and I'll come up with a solution for you.