Having a pocket symphony in your head–or pocket, as it were–does you little good if your hands aren't on board. Fortunately, YouTube user freddym233 is here to help you train your head and hands with his series of free video guitar lessons. In this installment, you'll learn how to play D7b9 and Dm7b5 jazz chord substitutions on your guitar. Remember, the more you practice and the more theory you know, the better you'll sound and the better able you'll be to play what you hear. To start playing these substituions, take a look!