Also known as Patch Change, a type of MIDI message used for sending data to devices to cause them to change to a new program. Program Changes messages are channelized so they will only affect a device on a specific MIDI channel. These commands are used in all sorts of MIDI applications ranging from simply changing patches on a synth or reverb to controlling lighting systems. Software sequencers that appear to have the programs of your keyboard in them by name are in fact using program change commands that are known to pull up those programs in your keyboard.