Adding sound to your video

Making videos is tricky, but adding sound to them can be even trickier. I thought I would share some things I have learned over the years.

Finding Sounds

You need to have sound files before you can do anything. Disclaimer: I am not a content-rights lawyer, so I cannot comment on the legality of some of these methods; they may or may not be covered under fair use or some other content rights.  I am merely describing what is possible; I am not endorsing or advocating anything. Employ them at your own risk.

• Use freely available sound samples. I have had good luck with freesound.org and Youtube in the past; just make sure to read the licenses.
• Record it yourself! You probably have a microphone, and voice modulator software is freely available to download. You can also sample sound effects; the internet is full of foley tutorials.
• Commission/request someone else to do it. Some of the samples I've seen on freesound seem to be requests from their forums. I'm sure there are many other similar sites out there.
• If you play a lot of computer games, you may discover you already have a bunch of sound files on your hard drive. Sometimes they will be mashed together in archives, but most games use standard archive formats, and many popular games have modding communities that make extraction utilities. 
• The internet is full of free videos. Some do not have background music. With freely available software, one could sample audio from these.

Mixing Software

Once you've acquired enough sounds for your video, its time to mix them with the video. You'll need some tools to help you. I use Adobe Premier, but there are plenty of options out there. I believe both iMovie (mac) and Windows Movie Maker (win) are free, and should be able to get the job done.
Some tips:

• use different channels/tracks for different purposes; 1 for each character, 1 for ambient/background music, tracks for different types of sfx. This will help keep you sane
• Experiment with filters: slowing down/speeding up, adding echo, changing pitch, reversing, etc. You can create new content with your existing content
• I prefer to export audio only from Premier and then combine it with the video separately, but these programs can output video as well.

Other Tools

Here are some other tools I use and what I use them for. These are all free

• Virtual Dub - add logos/censored bars to video, combine video and audio, convert between different formats
• Winamp - more support and conversion options for audio files
• AviSynth - Append multiple video files together
• DVD Video Soft Video to Flash Converter - converts video to flash format, which can be uploaded to DA