Quality or timbre of a musical note
If a particular note on a scale is played on, say, a piano and a flute, it is easy to distinguish the tone of one instrument from that of the other. The two tones are said to differ in quality or timbre.
Generally speaking instruments do not give tones which are pure in the sense that they consist of single frequencies only. In the majority of cases a musical note consists of several different frequencies blended together. The strongest audible frequency present is called the fundamental and gives the note its characteristic pitch. The other frequencies are called overtones, and these determine the quality of the sound.
The notes of a trumpet possess a quality derived from the presence of strong overtones of high frequencies, while the flue pipes of an organ have a mellow tone. In the case of the latter, practically all the sound energy is centred in the fundamental frequency and the overtones are fewer in number and of smaller intensity. Much experience and craftsmanship go into the design and construction of a piano with the aim of suppressing unwanted overtones and enhancing the desirable ones. The same can be said about other instruments, particularly the violin.