AudioJungle is a large scale music marketplace where users can both buy and sell royalty-free music and sound effects. More 128,000 number of tracks as available. Some audio tracks are made for looping, which means a 2-minute track could be repeated for 10 minutes without any noticeable gaps. As one of the Envato services it benefits from a hugely active community. You can search by music genre and by type, and all audio files have great visuals attached to it. You can find both audio tracks and sound effects (SFX) on Audiojungle.
Pricing: between 1$ and 20$