I have sample sketches working separately with the mp3 module and the rotary encoder.  The next step is to get them working with some sort of visual indicator.  I think I have enough analog IO to push a 7 segment display.

Where do you find a panel mount xlr connector, a 1:1 audio transformer and a project box for $8?  In a pyle di from amazon.com!

I was going to leave the transformer on the pcb but I need to relocate it to accommodate all the  other bits…..

http://www.amazingtips247.co.uk/2015/11/how-to-play-sound-tracks-with-catalex.html

http://bildr.org/2012/08/rotary-encoder-arduino/