I have some piano music on midi files. Some of the files are louder than the others. How to reduce the volume on the midi music? and re-save the file?. I don't mean to change the volume control of my speaker, but to reduce the sound volume at the file source. What kind of softwares (freewares) that are available to manipulate the midi files? I like to use the files as a background music and don't want to be too loud. Thanks for information.