As a musician and an attorney, this area to me is a complete crapshoot (a technical term.

) Take the 50s and 60s and doo-wop era as an example of the huge gray area. Thanks to that era my need to expand my repertoire was limited to remembering lyrics.

Yet "My Sweet Lord" resulted in a lawsuit between George Harrison and the Chiffons. Go figure.
But if the melody line is completely different and there are just general similarities in terms of the style, I'd say there is limited to no chance you'll have a problem. Don't take my word for it here - I haven't heard the song - but there are some things that are either not protected under copyright or not feasible to prove. Simply because a famous musical piece uses a quartet and happens to have 3 guitars which create a somewhat unusual ensemble doesn't mean that there is intellectual property protection with that group of musicians. Musicians make music together. Simply because one combination of musicians is less popular than another doesn't grant monopoly status on that combination and, if there was protection, it would have to be shown how copyright law applies in this situation. Moreso, how would someone go about proving infringement in this instance if the melody is different? Infringement of what? How many other pieces use the same style? My feeling as an attorney for the plaintiff - unless the combination is so exceedingly rare and unique so as to make copying highly likely, I wouldn't bother with the case.
My feeling is also that only very famous musicians get sued because they have deep pockets to sue. Everyone else flies under the radar unless their song becomes extremely well known. And unless there is a good connection between the songs, and not just a similar musical combination and some style that is representative of an entire genre of music. In the My Sweet Lord / He's So Fine case, the George Harrison and Chiffons songs contained some similarities but, to be honest, I don't think I would have given them a second thought without the lawsuit. To bolster my feelings on the topic, apparently the Billy Preston version of My Sweet Lord flew under the radar. But when one of the most well known names in the music business performed the song, people flocked to hear it and the trouble began.
Just my feelings on the topic.

Long live the creative process.