Almost everyone can play or sing middle-C. frequency-As stated above, when air waves occur in repeated patterns, hundreds of times a second, then humans hear the waves as having pitch. For example, if you play middle-C on the piano you will be creating air waves that repeat 262 times per second. The frequency of a sound is the exact number of times per second that a wave is repeated. Higher pitches will have higher frequencies. The most important frequency to know is A-440. This is the primary reference pitch (designated with the letter A) or frequency (440 times per second) which is used to tune instruments. You will hear the oboe play a note of A-440 when an orchestra tunes before playing.