Each of the five separate plugins in the Captain Plugins suite is dedicated to generating MIDI note data for a particular track component. While Captain Drums is the least compelling of the bunch from a songwriting point of view, and Captain Play is essentially a simple chord generator and key/scale limiter, Captains Chords, Melody and Deep work together as a brilliantly interconnected system for creating cohesive bass/chord/melody combinations.

Source: 5 Essential MIDI Plugins — Cool Utilities To Check Out | Production Expert

The Captain plugins are from “Mixed in Key”, the software outfit that Daniel Jalkut (MarsEdit) was working for.