Robin is probably right, tremolo is a more appropiate term to define the sound obtained by variation in pitch, which is the pleasant sound that we hear in classical singers and most of (good)pop singers (not exaggerated). It is the same effect as heard in the violins, cellos etc. It certainly comes with age. Voices with no vibrato (or tremolo) are typically those of children, they are are called "white voices", and you can dramatically hear the difference between a song sung by children and the same sung by mature women. Which one sounds better, depends on the type of song and personal taste. In a Haendel's oratorium, I will always prefer soprano and mezzo voices, and not children voices which could be very sweet but lack a lot of expression.

Exaggerated tremolo in old people comes more from the poor control of the diaphragm than from the vocal chords, producing a variation of air pressure which results in a wide variation of pitch, very unpleasant, and responsible of the existence of so many people who hate Opera. I love Opera, but I can't stand opera goats who are still singing because one day they were famous.

Ethereal Purple will have to wait some years. In the meantime, please don't follow misleading techniques of pop singers, especially nasal singers. Try a classical teacher, and once you get a satisfactory technique, sing whatever you like.

Un abrazo
Andrés (in Buenos Aires)