Running an LSTM with Music Data
You should ask yourself - are you teaching an algorithm to play chords or to play music? In addition, what are you trying to predict here? 

It seems to me that you need to create input data that is a series of chords and your label is the next chord in the tune. So you should design a neural network that takes in a series of chords and can tell you the next chord in the sequence, add that back to the input sequence and pick the next chord, add that back to the input sequence, etc, etc. Next thing you know, you have a neural network that can play music.