@ sarah ... u are correct... 4 at best is xtina's range. The modern Piano has 7 or 7.5 octave note range and she can not sing the width of a piano from bass to whistle notes. Singing up to a note in the 6th octave does not mean u have 6 octave range. Range is from ur lowest to highest note. Middle C is called C4.... so from C4 up to C6 is Two octave.... from C4 to C2 is 2 octaves down and I know she can not sing in Barry White's vocal range.