Free and Royalty-Free Sound and Music for Audiobooks, Trailers, and Video
A book trailer, an audiobook intro and outro, or a promotional video for social media all benefit from sound design, and none of it requires a music budget if you know where to look. The catch is that "free" audio carries more licensing nuance than free fonts or free images, because music and sound effect licenses commonly distinguish between personal and commercial use in ways that aren't always obvious at a glance.
The License Distinction That Actually Matters
Audio sourced under Creative Commons licensing generally falls into a few categories, and the distinction between them determines whether you can legally use a track in something you're selling or promoting commercially. CC0 is the cleanest: true public domain, no attribution required, no restrictions. CC-BY permits commercial use but requires you to credit the creator, typically in a credits page or description. CC-BY-NC is the trap: it explicitly blocks commercial use, meaning a track licensed this way cannot legally appear in a book trailer promoting a book you're selling, an audiobook you're selling, or any other commercial use, regardless of how good it sounds or how small your usage feels.
⚠ If you're building any kind of audio library you intend to reuse across multiple projects, commit to filtering for CC0 specifically from the start rather than mixing license types. It's slower to find perfect matches under CC0-only filtering, but it removes the attribution-tracking and commercial-use questions entirely, which matters far more once you're producing commercial content at any scale.
Where to Find Properly-Licensed Audio
Practical Production Notes
Looping quality is rarely production-ready out of the box — most free ambient tracks aren't built to loop seamlessly, and you'll typically need to take a raw recording and crossfade-loop it yourself in a free audio editor like Audacity to avoid an audible seam every cycle, particularly for any background audio meant to play continuously
Track attribution carefully if you mix license types — a simple spreadsheet logging each file's source URL, license type, and attribution status is enough, both to build a proper credits section if required and to maintain a paper trail if provenance is ever questioned
Match the energy of the audio to its actual use — a book trailer benefits from more dynamic, emotionally-driven music than an audiobook's brief intro stinger, which usually works better short, simple, and unobtrusive so it doesn't compete with the narrator's voice that follows it
Keep promotional video audio royalty-free even when posting to platforms with their own built-in music libraries, since platform-provided tracks are typically licensed only for use within that specific platform and may trigger content claims if reused elsewhere, such as repurposing a TikTok video's audio into a YouTube upload
A Note on AI-Generated Music
AI music generation tools have become a viable option for original, royalty-free scoring, and the licensing landscape here is evolving quickly. As with AI-generated cover art or other AI tools referenced elsewhere in this resource library, terms vary meaningfully by provider regarding commercial use rights and ownership of the generated output, so confirming the specific platform's current commercial terms before using AI-generated music in anything you're selling or promoting is essential rather than optional.
Conclusion
Sound design for a book trailer, audiobook intro, or promotional video is genuinely achievable on no budget, provided you're deliberate about license type from the start. Freesound.org filtered to CC0 is the simplest, safest default for most authors, with YouTube's Audio Library, Pixabay, and Mixkit as solid supplementary sources, and NASA's archive as a genuinely excellent niche resource for anything mechanical or space-themed.
- Randall