1(Book). Following in the footsteps of the popular Hal Leonard Pocket Music Dictionary, this handy pocket-sized book is the most contemporary music theory book on the market! A step-by-step guide to harmony and theory for every musician, it includes thorough, yet to easy-to-understand analysis of: intervals, rhythms, scales, chords, key signatures, transposition, chord inversion, key centers, harmonizing the major and minor scales, extended chords, modulation and much more. Packed with info from the Harmony & Theory course at Musicians Institute!