Yes, it actually is sol: it's traditionally written that way when the tonic notes are spelled out, and often referred to colloquially as the Solfa or Solfège scale. That final L is hard to hear Do = Tonic , Ra = Supertonic , Me = Mediant , Fa = Sub-dominant , So = Dominant ' La = Sub-mediant ' Ti = Leading note , Do = Tonic for whichever diatonic key you choose. .

do re mi fa so la ti do in letters