Since I began assembling book trailers, I have learned a few things. First and most importantly is copyright issues.
Many people think it's okay to pick your favorite song and just use it. Just throw some images together you find online and pair it to your favorite jam and post it online and everything will be okie dokie.
Unfortunately, as much as I'd love to use a Red Hot Chili Peppers' tune or a Tori Amos haunting melody, I can't. Not if I want to break copyright laws and potentially put myself at risk with the law enforcers. And/or not unless I want to spend LOTS of money to obtain the rights to that particular song. But let's be real here, no one in their right mind should spend that kind of money to market a book via a book trailer.
So what do you do? Where can you go to find songs that you can legally use without fear of running into copyright law infringements? Well luckily, there exists stock audio sites that allow you to purchase the rights to a song (usually for a single time use). What I love about these types of sites is that there are many quality musicians posting their work out there for you to buy for a generally inexpensive price.
My go-to site is audiojungle. For all the trailers I create, I look for a one to two-minute-long song, which costs roughly $14. Anything longer than two minutes and the prices increase by a few dollars. Just do yourself and your viewers a favor and don't bore them. Anything longer than two minutes and most people are hitting the snooze alarm.
There are many other stock audio sites as well:
istockphoto images and audio content you can purchase the rights to
pond5 images and audio available for purchase
audioblocks all audio
audiomicro all audio
freesound all audio
free stock music all audio
Even YouTube has a library you can use (with limitations).
While these are just some, there are plenty more out there. You just have to do a little digging and you can find a unique song to help translate your novels theme or feel. Did you write a horror novel? Well there are plenty of creepy tunes for you to pick from. A love story? Even more to navigate.
If you are going to market your book using music, do it right and legally. Find the song that will enhance and sell your book. Nothing kills a book trailer faster than a boring song. If you pick quality music your viewers will stick around to watch the entire trailer, I promise. If you pick a boring melody, your viewers will have moved on within 15 seconds.
--Sheilah G. Randall