Youtube does not allow audio files to be uploaded. However, you can easily convert any audio file into a video file using the given audio file and a fixed image as a background. The following works on Ubuntu and any variants of GNU/Linux.
For converting a single mp3 file you can use the following.
ffmpeg -v quiet -i "picture.jpg" -i input.mp3 -shortest -acodec copy output.mp4; done
For converting a batch of files in a folder you can use the following
