MIDI (Musical Instrument Digital Interface)

The MIDI Control dialog enables you to set up Amazing Slow Downer's response to MIDI input so you can use MIDI messages to control the playback of Amazing Slow Downer.
You may execute any command that have a keyboard shortcut in Amazing Slow Downer.

To control via MIDI you need to have a MIDI input on your computer and you need to have some kind of controller that generates a MIDI message. This could be a MIDI keyboard, the sustain pedal connected to your MIDI keyboard, a foot pedal or any device capable of generating MIDI messages.

MIDI Settings
The "Input" drop down menu lets you select what MIDI input port to respond to. To disable MIDI control, select the "No device selected" item.

The "Respond" drop down menu lets you select when Amazing Slow Downer will respond to MIDI messages.
"Foreground only" means Amazing Slow Downer will stop responding when another application is brought to the front, "Always" means Amazing Slow Downer will respond to MIDI events when in background as well.

Configuring
When you press a note or pedal you will see the MIDI message in the box labeled "Press MIDI unit for new command".
If this MIDI message is what you want, select a "Command" such as "Play" in the list box above and click the "Set" button.
To remove an item, select it and click the "Remove" button.

Some commands can be mapped to the same MIDI message, in particular controls that are meant to be controlled continuously such as "Volume Up/Down", "Rewind/Forward", "Raise/Lower Pitch" and "Decrease/Increase Speed" . These would normally be mapped in pairs or you might get strange behavior.

Hardware MIDI controllers with faders, knobs and data/jog wheels may generate their MIDI controller messages in several different ways but some are more common and here is how Amazing Slow Downer works for the following commands (this is a bit technical):

If you enable the "Jog" checkbox, the selected command will respond to MIDI controllers where the data value is in the form of "2's complement", with bit 6 as the sign bit. Positive numbers are sent for clockwise rotation. This is how most "jog wheel" works.
For example: 4 ticks clockwise rotation: B0 nn 04, 3 ticks counterclockwise rotation: B0 nn 43

If you disable the "Jog" checkbox, the selected command will respond to MIDI controllers with data values between 0 - 127. This is how most data sliders and faders work.

"Rewind/Forward" only responds to "jog wheel" controller data.

Note:
Amazing Slow Downer will respond to note on/off, controller and program change messages only.

Note that you may set a command for a note on event as well as different command for the note off (release) event.

All controller events less than 121 (except controller 64 to 69 - hold, sustain etc) are continuous meaning you might use them to control the volume, rewinding, speed change etc. Controllers 64 to 69 are switch events and react to two values only (sort of on/off) and are better suited for toggling playback etc.

To get familiar with MIDI , please read more here:
What is MIDI?
The MIDI Specification