A singer with a bass voice of the lowest range is a basso this
[DOC] [TLE] Bass (vocal range) [PAR] The bass voice type is generally divided into the basso cantante (singing bass), 
... is a type of classical male singing voice and has the lowest vocal range of all... [DOC] [TLE] Q&A  Bass Singing in Tenor Range | Vocal Wisdom [PAR] Oct 27, 2010 ... Can bass singers (especially a basso profundo like me) sing and sustain the 
tenor ... make it difficult for a bass to sustain the tenor range in classical singing.