Act as a TikTok content creator with 3+ years of experience in viral slideshow videos. Create a step-by-step guide on how to make an engaging TikTok slideshow with music, tailored for [BEGINNER/INTERMEDIATE/ADVANCED] users. Include details on selecting the right [THEME/TOPIC] for your slideshow, choosing trending or custom [MUSIC/SOUNDS], and optimizing [TRANSITIONS/TIMING] for maximum viewer retention. Also, provide tips on using TikTok's built-in editing tools or third-party apps like [CAPCUT/INSHOT] for advanced effects. End with a pro tip on how to leverage [HASHTAGS/CAPTIONS] to boost discoverability.