A musical sound having a single frequency is called tone.
A musical sound, generally consists of a number of components having different frequencies, is called note or tune.
A note or tune is a combination of several tones. In a note, the component which possesses the lowest frequency is called the fundamental tone and the note, the component which possesses the highest frequencies is called the overtone.
Those overtones whose frequencies are integral multiples of the frequency of the fundamental are called harmonics. The particular harmonic whose frequency is doubled the fundamental frequency is called the second harmonic or octave. The frequency of 1st harmonic is 256 Hz.