From Richard Marlow 24 May 2023: “Not sure if it is useful or you would be interested to discuss, but I came across primary source evidence of two humanist poets who played vihuela or Lute or guitar (depending on definitions). Benito Arias Montano is quoted as paraphrasing and singing specific psalms using the “citharae” in latin, as a sort of “mental health medicine” due to stress in the early 1550’s. He is also supplying a poem to Fuellana’s vihuela book. Also his friend/mentor/colleague Fray Luis Ponce de Leon has a poem describing singing with chords/strings, of the “laud” (probably written in prison, hence the “stress” of the time period due to inquisition not keen on humanist stuff). Both leave vagueness to melody perhaps, but relevant to your article I think. I have some ideas to what melodies might be at play if interested (it is a can of worms, just to warn you.)”
See https://en.wikipedia.org/wiki/Benito_Arias_Montano