To this great artistic service he was fitted by both the qualities which have been pointed out above as co-operating to form his unique nature. His deep and simple human feeling, which put him in sympathy with the aims of the romanticists and enabled him to grasp their meaning, would not have sufficed alone; but fortunately it was associated with an almost unprecedented scope of intellect and power of synthesis. Brahms's assimilative faculty was enormous. Like a fine tree that draws the materials of its beauty through a thousand roots that reach into distant pockets of earth, he gathered the materials of his perfectly unified and transparent style from all sorts of forgotten nooks and crannies of mediæval music. Spitta remarks his use of the old Dorian and Phrygian modes; of complex rhythms that had long fallen into disuse; of those means of thematic development, such as augmentation and diminution, which flourished in the fifteenth and sixteenth centuries; of «the _basso ostinato_ with the styles pertaining to it--the Passacaglia and the Ciaconna;» and of the old style of variations, in which the bass rather than the melody is the feature retained. «No musician,» Spitta concludes, «was more well read in his art or more constantly disposed to appropriate all that was new, especially all newly discovered treasures of the past. His passion for learning wandered, indeed, into every field, and resulted in a rich and most original culture of mind, for his knowledge was not mere acquirement, but became a living and fruitful thing.»