This German theorist composed works for the stage and the keyboard but he was much more respected as an improviser on the organ and for his controversial theoretical work. In his hallmark treatise, "Tonwissenschaft und Tonsetzkunst," Vogler argued many important points including the distinction of the triad and key modulations. All chords can be structured and ascertained from the root position triad, when the tonic note of the key signature is the lowest note of the chord and the intervals above it are respectively a third and a fifth. This being the case a root triad can be used to modulate to four other chords or keys. "C", as the root, can be used as a major triad in modulations to both F major and F minor and C minor, likewise, can be used to modulate to F major and F minor. Vogler also had a gift for understanding the colors of instruments achieved from their various timbres and scorings. In this, and his theoretical work concerning modulations, he laid the foundations, anticipated and essentially helped to forge the Romantic movement in music. Though not considered a great melodist he was an excellent improviser by the consideration of many with the exception of Mozart. Vogler's progressions, regardless of his lack of melodic gifts, were innovative and daring. Though his compositions are harmonic at best and both his theoretical works and didactic works demonstrate this, Vogler was considered an excellent organist giving over two thousand concerts during his life and continuously promulgating the ideas of organ reform. Together with his positions in service, first as a chaplain in the Mannheim court and later as the Kapellmeister of Munich, Stockholm and Darmstadt, Vogler had a profound impact on the development of music. As a teacher he perhaps echoed the influential strains of his own teacher in Italy, Vallotti, by having effected other great musicians like Weber and Meyerbeer. ~ Keith Johnson, Rovi