Yes, I'm here....
Kev's right.The cello of all instruments has the range that covers the human voice and it can be very expressive. Unamplified, compared to a wind or brass instrument, it is 'relatively' quiet (partly because of its timbre) which is probably part of the reason it wasn't really used in that capacity.
It is mostly used in conjunction with other instruments to provide backing harmony and rhythm.
In terms of sax pitch range, the cello covers bari, tenor/alto ranges.
The cello plays at concert pitch (no transposition required, i.e. "in C") and uses bass clef. Many real books (and others such as the Aebersold ones) can be bought, which contain the music in bass clef in "C".