However, there is an infinite variety of sound events whose form is periodic but differs from that of a sinusoidal signal. They consist of a fundamental with superimposed harmonics, and the number of harmonics, their frequency, phase and amplitude can be completely different. If the tone has harmonics or if several tones are emitted together, it is a mixture of tones or a sound. For example, instruments produce a mixture of tones from the fundamental and the superimposed harmonics. Only by combining the fundamental and harmonics can the sound of different instruments be distinguished from one another.