I'd like to make be able a project file only ninety seconds, and have Ableton discard any music that runs over that time as a result of any midi tranformations or effects.
- Go into arrange view, expand the master track
- Enter draw mode: press ctrl+b or click on the pencil button at the top of the screen next to the little keyboard. You want it to be yellow.
- Use draw mode to zero out a region of the Master Mixer - Track Volume automation
- Exit draw mode: press ctrl+b again, or click on the pencil button so that it is no longer active.
- Use the pointer cursor to click on one of the automation corners to the right, deleting it.
- Delete the other rightmost automation corner. Now the automation curve should be down at the bottom for the rest of time.