I know this topic has been touched on several times- the limitation of Ableton in that for many controllers, in can only recognize one message, e.g., note in but not note out when mapping to devices. In order to chop audio on the fly for example, you need to translate each of those to the same message somehow. This is a video tutorial showing my workaround using Midipipe (free download) to create a key split and then two message converters to achieve this.
No disrespect to the others who have posted solutions to this, I just figured this option might strike some as simpler or easier to configure. Still took me 12 minutes to demo and explain everything