"I don't sing because I can't carry a tune... I do sing along with others because I can match their notes."

Pauline, I think that article is about you. You sound intimidated & performance oriented. If you can match pitches that's singing in tune. Why should you feel otherwise? There are a lot of people who have difficulty staying in tune (same key) when singing solo. If you don't sing a lot, it may just be that you don't really know the tune well enough to do it alone. Singing does not necessarily mean solo singing.