Here’s a quick rundown of what the different options in the MIDI Sync pane in the Preferences dialog of Ableton Live (8) mean:

Control Surface

This section is where you set up your auto configured devices. An auto configured device is a device that Live already knows about and has a preset mapping for. Examples include the Novation Launchpad and the Akai APC20 / APC40. Live as an extensive list of auto configured devices so if you are hooking up a new MIDI controller it is always a good idea to check this list first. You will save your self a lot of head ache if your device is listed here. If you are a dedicated Live user looking to expand your line up of MIDI controllers you could also use this list as a starting point for deciding which controller to get.

Input

Choose the same Control Surface here as in the Control Surface column to let Live receive MIDI from your controller.

Output

Choose the same Control Surface here as in the Control Surface column to let Live send MIDI to your controller.

Takeover Mode

The value of this drop down decides how Live deals with incoming MIDI values from a controller, that does not match the current software setting in Live. For example, if you have moved a fader in the software and your hardware controller’s fade now is in a different position, if you move your hardware fader the MIDI value coming in to Live will be very different from the current software value of the fader. In this scenario, Live can do one of three things:

1. None: Jump directly to the incoming MIDI value. This could mean a sudden, large change in value
2. Pick-Up: The value in software will not change until the incoming MIDI value matches it. At this point the software will ‘Pick-Up’ the incoming value and start to update to reflect it. In reality this can lead to control fiddling while ‘searching’ up and down a fader for example to find the current value in software.
3. Value Scaling: With this setting, Live will compare the current software setting to the incoming MIDI value and calculate a gradual transition as you move your hardware control. When the two values match Live will move the software value in a 1:1 mapping with the hardware control again. (This is usually the best option, but it can make it hard to do sudden parameter changes when this is desired.)

MIDI Ports

In this section you can manually configure controllers that do not have any preset configuration with Live. The MIDI Ports column lists all the I/O ports (usually devices) that Live is aware of. You will usually see each device listed once for Input and once for Output, which basically corresponds to the Input / Output columns in the Control Surface section explained above. Depending on how you plan to use your device, you will need to enable a combination of the three values listed next to each controller. Below is a short explanation of what they all do:

Input / Track

If you wish to be able to record MIDI notes from an instrument into Live, this setting must be On. This lets you select the control surface for the instrument in the MIDI From drop down list on your MIDI track, and you can then record MIDI clips from your external gear.

Output / Track

If you wish to send MIDI notes from a MIDI track in Live to an instrument you need to set this to On. Doing so lets you select the controller in the drop down lists for MIDI From and MIDI To in the MIDI track settings (for each track). Remember, if you want to sequence a hardware instrument via a MIDI track in Live, you will need to set this setting to On.

Input / Sync

Just as Track controls the sending and receiving of MIDI Notes, the Sync options let’s you configure Live to receive MIDI Sync (clock) messages from external gear. This is helpful if for example Live controls a set of software instruments, but the clock source in your setup is coming from an external instrument / controller that also manages the MIDI clock for other external gear.

Output / Sync

Just like Input / Sync Lets you control Live’s clock via external gear, you can also control the MIDI clock of external instruments from within Live. Put this setting in On mode to send MIDI Sync (clock) messages to your external gear.

Input / Remote

Enable this to let Live receive incoming MIDI control messages from your controller. If you want to control parameters or send MIDI control messages to Live from an external device, this setting must be On.

Output / Remote

Enable this to have Live send MIDI control messages to your controller. If you want your controller’s visual indicators or other parameters to reflect changes in the Live software, this setting must be On so that Live sends the necessary data to it.

Finally, keep in mind that you can learn most of this (and much much more) from within live by opening the Help UI box and hovering over the options in the Midi Sync pane of the Preferences dialog. Also, Ableton has a great FAQ about using MIDI in Live.