download how to use casio ctk 574 keyboard as a midi controller native instruments maschine mk2

The 'Audio In' jack you refer to in your post is for connecting the audio outputs of a stereo unit or MP-3 player or CD player, etc for playback through your keyboard's sound system and speakers. Then, in any of your software (FL Studio, etc) MIDI set up menus, you will be looking to select a MIDI device shown as 'CASIO-USB-MIDI' or something similar to that. Just connect the cable, power up the computer, then power up the keyboard, once the computer is fully up and running - truly 'plug-n-play'. Casio keyboards are now what we call 'Fully Class Compliant' (Windows) and 'CORE MIDI Compliant' (Apple), meaning that they will automatically work with the standard USB-MIDI drivers that have been built into Windows since XP Service Pack 2 and the last several versions of MAC-OS and iOS (iPad/iPhone), so you will not need to install any special drivers. See of your manual for instructions on connecting it to a USB port on your computer.

It uses what is commonly referred to as a 'standard USB printer' cable that can be found at just about any retail outlet that sells computer equipment/supplies. It is bi-directional, so it serves the purpose of both MIDI IN and OUT. That is now your MIDI connector, commonly known as 'USB-MIDI'. Look at the lower half of of your manual for a diagram of the connectors on the back of your keyboard.

Casio no longer includes the old 5-pin DIN (round) MIDI connectors on their CTK/WK model keyboards.

Download how to use casio ctk 574 keyboard as a midi controller native instruments maschine mk2