Ableton Live's Scale device restricts all MIDI notes to a defined scale - it's a great way to ensure that what you're playing is always in line with what you'd like. You can also use Scale to explore new scale sets, including ones you may not have experienced before. Tobi Hunke, the organizer behind the Ableton User Group in Göttingen, Germany, has released a free downloadable set of 40 presets for Scale. Learn more in this video: 

Download the Scale presets here. You can also keep up with Tobi on his blog.