The Harmonic Series http://www.middlehornleader.com/Overtime%20Series%20copy.jpg The Harmonic series is a series of multiples of a base frequency. The harmonic series of a trumpet are the set of notes that can be played without valves.                                                                                                                                                                                                                              http://hyperphysics.phy-astr.gsu.edu/hbase/waves/clocol.html On a string or air column that is open at both ends, the harmonic series are even multiples and the contain the main octaves. As you increase the frequencies, the number of nodes increases, as seen in the left in the figure above. The right figures represent when the string or air column is open only at one end. You get a different series because the ends are anti nodes rather than nodes. The frequencies also have to be increased by much more to reach the same resonant points. They also end up  as an odd series. The trumpet is closed at one end by the mouth and therefore follows this pattern.  As is characteristic of both types of harmonic series, as the notes become higher, they grow closer together. This is why before valves, the horns were usually much longer, so they could reach a wider range of notes. Each note we hear in the series represents the strongest frequency at that point. The are made up of a culmination of many other frequencies. These are overtones which gives the trumpet its rich sound. It is important for an instrument to produce the full harmonic sequence. The closed tube of the trumpet produces only odd harmonics, so to adjust the sound the instrument makes, the shape of the bell and mouthpiece had to be altered. Home History General Physics  The Harmonic Series Parts of the Trumpet Bibliography