I have 2 questions based on Content which I am quite puzzled about and I hope someone experienced can advise me:

1. I have read in a number of places than relevancy is crucial. However, how does this positively or negatively affect your site? For example, lets say your site is based on headphones. If you were to publish an article about Jay-Z's new album how would this affect your site. Music is obviously a major part of headphones but how does Google decide this is relevant or irrelevant?

2. Some of the most popular blogs publish articles purely based on innovation and hot trends as it is naturally able to grab peoples attention. But can content based on cool subjects help boost a sites popularity. For example, if your site is about headphones and you publish a blog post about 3D printed headphones could this help to get retweets and links.