Whats the difference between Master & Slave?

If you need to buy a plug MPCLove86, here are the specs -

Input -120V AC 60 Hz

Output - 9v DC 500mA

Polarity - you'll need the positive polarity on the left side of the diagram stamped on the plug specs, or get a plug with a switchable plug that does both and match the left picture orientation.

I have a MIDI UNO essentially just a different name which has a midi in and midi out male pieces that go into this little oval shaped piece attached to them. Out of the other end is USB. Thats what I have the mpc hooked up with into ableton. The other midi cord I have has 90 degree angle on them and wont plug into my keyboard because theirs a piece in the way so the midi plug wont place correctly. So this is why my keyboard is hooked up usb into ableton. I figured I could adjust a setting or something to allow it to record into the mpc. I have a power cord for the keyboard so I just need to get a better midi cord. I also have a midiman midi sport 2x2, I found working drivers for it so I just need better cords. Plus I dont even really need it considering the midi uno I have. Again much appreciated for the responses. Have been working slot finally have a day off to play with it.