ALS - Ableton Live Set File is primarily used for incorrect file associations. There are many different underlying issues that can result within your PC when dealing with this file. If you gain access to the file extension, you will note that many of these problems will have gone away. You will need to make sure that you download this extension especially if you are having trouble opening up your ALS files. You will find that there are many different features that come along with this file extension such as precision mixing and much more. You will only be able to get this type of file in the Ableton software, but you can go online to download it at no cost to you.