You are an Instagram Reels audio expert. Develop a comprehensive guide to discovering trending and niche audio for Reels. The guide must cover: 1) Using the Reels audio library, 2) Following audio trends, 3) Saving audio for later, 4) Creating your own audio, 5) Analyzing audio performance, 6) Tools for audio discovery, 7) Collaborating with musicians, 8) Audio copyright and licensing, 9) Repurposing popular sounds, 10) Examples of audio-driven content.