I see that in the original printings of renaissance vocal music, the voices are labeled with Latin words like cantus, triplex, medius, etc... Assuming that these words denote the ranges of their respective voices (the same way soprano alto, tenor, etc. do), what are those ranges?
These terms did not designate vocal ranges; rather, they designated relationships between the various parts.
- Voice-parts. The following designations of voice-parts are found in MSS. [manuscripts]: Cantus, discantus, superius, triplex, medius, altus, contratenor, tenor, bassus, quintus, sextus. These should not be taken to be descriptive of the character of the voices, but only of the relation of voices to one another. Their relative position is shown by the meaning of the names.... Tenor was the part that held the plainsong. Bassus [was] always below it.... Above the tenor sang the cantus or discantus, and above these again superius or triplex.... Medius was a voice between triplex and tenor. The name of altus may have been given to indicate a voice that was high in relation to the tenor or deep in relation to the triplex. Contratenor describes a voice in close juxtaposition to the tenor, originally either above or below, but by the sixteenth century always above it. Quintus and sextus were used of a fifth or sixth part whatever their positions; a quintus book may be expected to contain a voice which doubles any other part.1
During the Renaissance, pitch notation was not standardized in the way it is now. The actual performance pitches were determined by the ranges of the singers on hand.
historic accounts of choosing a pitch according to the capabilities of the available bass voices and transposing polyphony so as to align the tenor part with the octave in which chorale melodies were customarily sung.2
1From Tudor Church Music, ed. Buck, Ramsbotham, et al. (Oxford University Press, 1923-24), page xlv. (emphases mine.)
2Andrew Johnstone, "The Performing Pitch of William Byrd’s Latin Liturgical Polyphony: A Guide for Historically Minded Interpreters", REA: A Journal of Religion, Education and the Arts, Issue 10, 'Sacred Music', 2016 (page 1).
Sorry to just cut and paste a definition. Maybe a ancient music scholar will post a more in depth answer. I found this footnote in a book of Tudor vocal music. It seems like a good starting place. Apparently the terms are less about range and more about the role of the parts - ex. tenor sings the plainsong - and their relative relationships within the ensemble.
[https://books.google.com/books?id=aNuQqBrh9G4C&pg=PA5] Tudor Church Music: John Taverner, pt. 1 Carnegie United Kingdom Trust, 1923
8 Voice parts The following designations of voice parts are found in MSS Cantus discantus superius triplex medius altus contratenor tenor bassus quintus sextus These should not be taken to be descriptive of the character of the voices but only of the relation of voices one to another Their relative position is shown by the meaning of the names whose origin must be sought far back in the history of music Tenor was the part that held the plainsong Bassus always below it may even be the lowest of three trebles Above the tenor sang the cantus or discantus and above these again superius or triplex The latter originally the highest of three is always the top part but loses its precise significance with the intrusion of voices between it and the tenor Medius was a voice between triplex and tenor The name of altus may have been given to indicate a voice that was high in relation to the tenor or deep in relation to the triplex Contratenor describes a voice in close juxtaposition to the tenor originally either above or below but by the sixteenth century always above it Quintus and sextus were used of a fifth or sixth part whatever their positions a quintus book may be expected to contain music sung by à voice which doubles any other part whether treble alto tenor or bass
This fluid nomenclature crystallized in course of time Old forms were discarded and certain of the titles became conventionally descriptive of character of voice By the time of Barnard 1641 medius had ousted all other names of the highest voice contratenor of that next below while tenor and bassus kept their places Where more than four voices were required one of these was doubled and the parts distinguished as first and second or assigned to the two sides of the choir the Dean's side and the Cantor's or Precentor's side the familiar Decani and Cantoris
In this edition the original names of the parts are given wherever it has been possible to do so without creating a babel of voices and modern equivalents are added in brackets below describing the character of each voice
Missing parts are supplied in the text and noted in the schedule of MSS used for each piece except when two or more parts are missing in which case the existing parts have been reproduced as found without any attempt at completion We do not profess to have been able to produce parts which the various composers would have written only such as fill the vacant spaces without offence In the case of Taverner the difficulty is extreme of making any approximation to his style and the attempt has only been made in order that his great music should not be left unsung for want of a component part The task has been somewhat easier with later writers in whom both style and idiom are more definite
These are just names sometimes (not lately) given to voice ranges.