The metronome is used for defining the tempo. An even pendulum produces a sound to define a certain beat. It was Johann Nepomuk Mälzel who developed the metronome in 1815. Modern metronomes use electronic signals. The number that is set on the metronomes scale indicates the number of beats per minute. Metronome marks can often be found as tempo recommendations at the start of a score.Beethoven was a strong advocate of the metronome. In 1818 he and Antonio Salieri argued for it in an advertisement in the musical paper Allgemeine musikalische Zeitung. He added metronome marks to some of his works. Today, however, these are often regarded as too fast.Beethoven works with metronome marks:All nine symphonies (op. 21, 36, 55, 60, 67, 68, 92, 93, 125);The first eleven string quartets (op. 18, 59, 74, 95);Septet op. 20;Sonata for piano forte op. 106;Op. 112, 121b and 137 as well as WoO 148 and 149;Planned (but not completed) were metronome marks for op. 123, 127 and 85.