It is important to note that all music instruments, including human voice are capable of producing only a limited range of frequencies, i.e. musical pitches. Human hearing range is usually between 20Hz and 20 kHz. As a general guideline, anything below 30-40 Hz is too low and above 5 kHz is too high. Piano is one of the most wide ranging music instruments, which is also perhaps the reason why most composers prefer Piano or Keyboard for compositions. The standard piano has 88 keys ranging from 27 Hz to 4186 Hz which pretty much cover the entire range of pitches which could be of musical interest.
Human vocal range is usually between two to four octaves. A range of two octaves is good enough for most songs. In fact several popular songs can be sung over a range of one and a half octaves.
Figure below shows indicative range of some of the popular instruments.