If you want to add your own music to the videos before uploading or sharing them without hassle, then try the WonderFox Free HD Video Converter Factory. This free video processing tool supports a wide array of input formats and offers 500+ output presets, which allows you to add audio to MP4, MKV, MOV, and other video files in a few simple clicks. With it, you will not encounter the format incompatibility issue! Moreover, it is 100% free, no size/length limit, watermark-free, and easy to use! Try it now!
* Before you put the audio track to MP4, make sure that the audio and video are of the same length to avoid any “audio out of sync” problems.
Step1: Free downloadFree download and launch Free HD Video Converter Factory.
Step2. Enter the "Converter" module and click "+ Add Files" to import your video files.
Step3: Press the format image on the right side to open the output format library. Choose a preferred output format under the "Video" or other tabs.
Step4: Click the "+" button next to the "Audio Track" section and add your own external audio tracks to the video. Then, from the "Audio Track" drop-down options, select or deselect the original track.
Step5: Hit the bottom inverted triangle button to specify an output path for the exported video. Finally, press "Run" to start exporting videos.