just add -i audio.mp3
to parameters, so the command will look like: ffmpeg -y -loop 1 -f image2 -i /image.jpg -vf 'scale=640:-1' -r 30 -t 10 -pix_fmt yuvj420p
-i audio.mp3
out.mp4
Also, here is a good answer: https://stackoverflow.com/questions/11779490/ffmpeg-how-to-add-new-audio-not-mixing-in-video
And here is a ffmpeg-audio manual: http://trac.ffmpeg.org/wiki/Encode/MP3