LS3 - Band-in-a-Box Third-Party Styles File is a file extension that can be used to create musical accompaniments. If you are already using Band-in-a-Box then you will be able to take advantage of this extension. It is also saved under a plain text format and consists of a third party seller in which you should be aware of. You can create different types of music from Rock to Jazz. It also uses .STY as a file extension but you must have the BiaB software already installed on your computer. This file extension is definitely worth using. It comes in handy when you need it the most.