Absolute pitch is the ability to reproduce an A or any other note requested without the aid of another sound. Relative pitch is the ability to reproduce any note once one note is known. Absolute pitch is quite rare; relative pitch is essential to a musician. There are musicians of all kinds, including singers, with absolute pitch and they seem to have it from birth. It is not essential to a musician, though it certainly is helpful. As suggested, most musicians have good relative pitch.

Remember, however, that pitch is set by convention. Since Bach, it has risen about a whole step. As late as the 1960’s, the difference between the US (A = 440 vibrations per second) and Austria (A = 446 vibrations per second) was such that an A in Austria sounded like a B-flat to me. To this day, not all countries and orchestras tune to the same, agreed-upon A. These differences require adjustment by all musicians and particular difficulties or opportunities, as the case may be, for singers.