Some of these Viennese pianos had the opposite coloring of modern-day pianos; the natural keys were black and the accidental keys white. It was for such instruments that Beginner Piano Lessons Wolfgang Amadeus Mozart composed his concertos and sonatas, and replicas of them are built today for appliance in authentic-instrument performance of his music. The pianos of Mozart's day had a softer, clearer tone than today's pianos or English pianos, with less sustaining power. The appellation fortepiano is nowadays often devoted to distinguish the 18th-century machine from later pianos.