The KeySwitch & Expression Map is a Max For Live device.
Max For Live is part of the Ableton Live Suite. If you use Ableton Live Standard you might have to buy an add-on license to use this device. Ableton Live Lite and Intro do not support Max For Live!Please find more information here:
The device was originally created in Ableton 10 with Max For Live 8.1.7
I tested it in Ableton 11 and it is 100% compatible.
Generally, it works also in Ableton 9 and Max For Live 7, but there are some bugs or functions missing you should be aware of:
The device has no effect on your computer’s CPU. Therefore, you can use it on any system and there are no hardware requirements.
However, if you intend to use the KeySwitch & Expression Map to work with many tracks and a lot of articulations for each VST instrument in your projects, I would recommend that you have at least 16 GB of RAM. Especially older VST players often preload a lot of a sample into the memory because there were no fast SSDs (Solid State Drives) in their days. This can quickly sum up to several gigabytes.
The device itself also requires about 65 MB for each instance due to the high number of parameter boxes in the KeySwitch Editor, so that you can comfortably create your key switches and easily change them at any time.
How did I measured that? I loaded the device into 100 tracks. Then I subtracted the approx. 500 MB for Ableton and divided the rest by 100.