What is this analogy Blank is to alto as tenor is to bass?

In this analogy, "blank" is to "alto" as "tenor" is to "bass." The relationship between alto and tenor is that they are both voice types within a choir or vocal ensemble, with alto typically singing higher than tenor. Similarly, bass is the counterpart to tenor, with bass voices typically singing lower than tenor voices. The analogy is drawing a parallel between the relationships of voice types within a vocal ensemble.