This promo is called “NBC Nightly News Hard & Fast”. It was used to promote a feature report on the next edition of Nightly News. Aside from main themes, networks commission promo material from a composer that they have under contract as a music producer. While promos usually feature the signature of the main theme, they are produced more cheaply: fewer live instruments and more synthesizers. And while main themes can be used for decades, promo music is refreshed every few years.