The first movement of Johann Sebastian Bach's 5th Brandenburg Concerto may be considered the precursor to all the piano concertos that have come along since this piece was written in 1721. Prior to this, harpsichords, being by nature soft voiced and non-dynamic, were only used as continuo, or accompaniment to more prominent instruments - violin, flute, horns. Even if there had been no Bach, the ongoing development of louder and more dynamic keyboard instruments such as the forte piano assured the inevitability of the piano concerto form, most notably seen, and heard by audiences in late 18th century Vienna, in the virtuosic piano konƶerts of W. A. Mozart.
Besides his compositional genius, Bach was also a highly gifted organist, stunning listeners of the day with his fusion of the tonal majesty of the most powerful musical instrument in the world at the time - the church pipe organ - combined with his own harmonically intricate compositions and lightning quick keyboard technique. He took that keyboard virtuosity, and transcribed it for the humble harpsichord, and the result was this concerto - listen toward the end of the first movement (above) and hear what the always forward thinking Bach imagined as possibilities for the future of the keyboard.
The always dynamic Cleveland Baroque Orchestra, Apollo's Fire, led by Jeannette Sorrell at the harpsichord, perform J.S. Bach's Brandenburg Concerto No. 5, BWV 1050. Movements 2 and 3 below: