In a class by itself is the wonderful Passacaglia in C minor, which Bach wrote as an advanced exercise (a practice piece!) for the two-manual and pedal clavichord. It consists of twenty variations on a _basso ostinato_ of eight measures. The theme is announced by the pedal alone _pianissimo_ and is repeated over and over again in one voice or another while the other parts build up a structure of ever-increasing elaborateness and magnificence, the whole concluding with a fugue whose subject is derived from the _basso ostinato_. The eight ‘Little Preludes and Fugues,’ so familiar to organ students the world over, were composed probably for his own numerous pupils. The six sonatas (or trios) of Bach were not written for the organ but for the pedal-clavier for the use of his son Friedemann. However, the wonderful three-part writing makes them especially suitable for reproduction on the organ and affords excellent opportunity for color and contrast in registration. They contain a wealth of musical ideas of varying moods, character, and deep expression, full of soul and life, and clothed in attractive and often playful technique, the highest of Bach’s art--a constant source of inspiration to the organist that will take the time to delve into their depths. They are not sonatas, of course, in the modern sense of the word. Of special value may be mentioned the following numbers from them: the first Allegro of Sonata No. 1 in E-flat, the elaboration of which approaches the modern sonata; the Largo and Finale (in reality a masterful fugue) of the Second Sonata in C minor; the whole of the Third Sonata in D minor, the Adagio being of especial beauty; the Andante and Allegro (Finale) of the Fourth Sonata in E minor, in the Andante the harmonic effects being so full and complete that one forgets that only three voices furnish the material; the Largo of Sonata No. 5 with its rich figuration work; and the first Allegro and the Largo of the Sixth Sonata in G major.