Sopranists are very rare, since most countertenors are altos and mezzos. The King's Singers consist of two countertenors, a tenor, a bass and two baritones. Some of the later revivals used countertenors in the roles written for castrati. The modern practice of approximating castrati by using countertenors as replacements only dates to 1950. Countertenors are also widely employed within opera as solo vocalists. Oberlin, however, harked back to the earlier tradition of countertenors using only their modal voices. By 2020, one of the countertenors had been replaced by a female alto. The instrument blends extremely well with male voices, particularly those of countertenors. The roles of Tolomeo and Nireno are normally sung by countertenors. However, these men are more commonly referred to as countertenors or sopranists. These do not fall into the female categories, instead called countertenors within classical music. Today, countertenors are much in demand in many forms of classical music.