If you know how to use sound file with HTML you can put as many sound, midis, etc. on you page as you want. To do it with HTML in page builder: click 'insert' > 'forms and scripts' > HTML code.
Or, if all you want is some background music: 'insert' > 'basic' > 'background music.
In both cases you will have to upload the sound files first. Or, use them off of another site, but most people don't like you stealing their bandwidth.