5.15 Summary of Section 5
It is probably worth summarising some of the main points you should take away from this section on primary vibrators. The first thing to remember is that when an instrument is excited, it vibrates strongly at certain frequencies called natural (or resonance) frequencies. The reason for this is that standing waves are set up in the instrument's primary vibrator at these frequencies. The next thing to note is that some primary vibrators, such as a string or an air column, have natural frequencies that are essentially harmonically related. Instruments containing these primary vibrators tend to produce notes that have a well-defined pitch. Other primary vibrators, such as a circular membrane, a circular plate or a rectangular bar, have natural frequencies that are not harmonically related. Instruments containing these primary vibrators usually (but not always) produce notes that do not have a well-defined pitch.