According to Dr. Daniel Robbins of minotaurz.com, Johann David Heinichen laid the foundation of music theory concepts including chord inversions, octave rules, interval and chordal classification and key signature reform. From 1753 to 1762 Carl Philipp Emanuel Bach discovered diminished and augmented chord and interval structures and documented these findings in his "Essay on the True Art of Playing Keyboard Instruments." These concepts help students identify chords and intervals played in music and translate them to instrument performance and different keys.
The Merriam-Webster Dictionary defines having a musical ear as the ability to learn music with the ability to differentiate off-key or off-pitch music. Catherine Schmidt-Jones and Russell Jones of Connexions Consortium say ear training does not focus on the organ's ability to recognize music but on the brain's capacity to perceive and understand what the ear hears. Ear training hones a musician's sound recognition aptitude and enables her to take what she learns and apply it to song composition, key transposition and playing by ear. Once a musician figures out the chords and notes played in a song, she can mimic the patterns on an instrument and reproduce the song without sheet music assistance.
Perfect pitch, or absolute pitch, is an enviable skill few musicians possess. Musicians with perfect pitch can identify exact pitches in music. This means they can differentiate when an A note or a C chord is played, whether the chord is major or minor and if it is played in the root, first or second inversion. Perfect pitch takes the guesswork out of piecing apart music and distinguishing chord variations, intervals and progressions, as notes and chords are identified correctly each time.
Reference.com defines relative pitch as the pitch of a tone determined by its relationship to other tones in a scale. This skill is more common among musicians than perfect pitch. Relative pitch enables ear trainers to identify whether a chord is major or minor, regardless of the pitch and key, and which chord progressions a song contains.
Instrumentalists employ various learning techniques during ear training. Some musicians rely purely on listening to music and plucking out chords on an instrument to figure out pitches and chord patterns. Others learn from ear training software, which presents students with a pitch or chord and gives instant score feedback. Still others work with trained partners, who play a chord or pitch on an instrument and provide students with "correct" or "incorrect" responses after identification attempts.