One good option is Tracksy, which is geared for creative types who want to make their own music without necessarily knowing how to do so. You can generate tracks based on a mood, with different track styles and lengths available. Tracksy offers HQ WAV and HQ MP3 formats for high-quality background music, and there are different pricing plans for different needs.
Another good option is Beatoven, which has two interfaces for generating music. You can type in a description of the background music you want (Text to Music) or select a genre, emotion and tempo to get the resulting music. Beatoven is geared for content creators who want background music for videos, podcasts and games, and it's designed to produce production-ready music that's easily edited.
Loudly and Boomy are also strong contenders. Loudly offers a large library of royalty-free audio tracks, loops and stems that you can search by genre, mood and other attributes so you can find the right music for your needs. Boomy has an interface that lets you create tracks for specific moods, genres or styles, and it's geared for content creators and businesses.