J.S. Bach understood to perfection not only the "possibilities" of all stringed instruments. He also profoundly understood the individual technical and musical character of each stringed instrument, as well as its limitations. Nowhere is Bach's holistic understanding of a stringed instrument more evident than in his six works for violoncello solo. Bach writes completely in harmony with the natural pitch, tone quality and pace of the violoncello. Vivaldi was progressive musically. He established the concerto form as an instrumental standard, played with the idea that the soloist was at war with the larger orchestra and using the contrasts to dramatic effect, he pushed the envelope on violin technique.