I'm responsible for SEO of a music service web site, and I'm planning on adding some new content to help users get more out of our service. This page will cover some FAQs (though not in as much detail as our comprehensive FAQ page), and will offer some tips and tricks on how to best use the service.

This page should get a good amount of traffic (~10% of the total page views on the site), and will see a decent amount of linking from other sites.

My question is, will the keyword density of this sub page affect the organic ranking for the main page, or will it only affect the ranking of the 'how it works' page itself? Thanks!

each page should have plenty of unique content...but other than duplicate content filters or how the pages effect your link structure one page should not hurt another based on it's keyword density or whatever...kw density is typically a bit useless to put much effort on because many people write robotic sounding pages when they think of it