So far we have talked about hearing and singing Do, Re and Mi. Let's review what we learned.
Do (pronounced like "doh") is the most stable sound. All other pitches in the scale sound like they want to go back to do.
Re (pronounced like "ray") sounds as if it wants to go back to Do or up to Mi. It is the least stable sounding of the three pitches.
Mi (pronounced like "me") is another stable sound. Mi has a weak pull back down to Do.
For a more complete review of Do, Re and Mi go to Hearing Do, Re, Mi Melodies.
Fa (pronounced like "fah") is the most unstable of the pitches we have learned. It has a very strong pull down to Mi.
So (pronounced like "Soh") is the second most stable pitch in the scale. Only Do is more stable sounding. It has a weak pull back to Do.