Question

What distinguish is the sound from two musical instruments even if they are of the same pitch and same loudness?

Answer 1

Sound from two musical instruments of same pitch and same loudness can be distinguished by their different quality or timbre. The quality of a musical sound depends on the wave form and the wave form of an instrument depends on the presence of the subsidiary vibrations along with the principal vibrations and the relative amplitudes of the various subsidiary vibrations in relation to the principal vibration.