fundamental tone 
noun Music
The tone which represents the fundamental frequency of a vibrating object such as a string or bell.The overtones, with their compound, irregular vibrations, give a fundamental tone a certain character or ‘clang-tint.’...
- We rarely hear a pure fundamental tone either in music or in nature.
- Such freedom of movement of a fundamental tone is specific to advanced written music of European origin, and in any case creates problems for the acoustic design of public buildings.