b>A Chord Key Encyclopedia Every chord in each key of music listed from most probable to least probable. Guitar: Probable Chords uniquely combines method and instruction with a guide for song writing for all styles of music. It also acts as a valuable reference for as long as you own and play the guitar. Chords for each musical key are listed from basic through intermediate and advanced based on music theory as well as "exceptions to the rules" based on all styles of popular and modern music. Like a chord encyclopedia, it offers every known chord. Unlike a chord encyclopedia, it shows a player how and where to use each guitar chord in music. Music Inc. Magazine. Book & CD.