It is often said ``Choral music must be tuned in Just Temperament but not Equal Temperament''. It is true that harmony on Just Temperament has good sounds. In particular, voice can flexibly change the tone rather than any other instruments. That is why, theorically, we can sing all notes with Just Temperament tuning.[Fundermentals of Temperament]
However, in actual, some long tones must be changed the tones themselves to realize the perfect consonant in Just Temperament tuning. We often hear that Music in Renaissance era must be sung with Just Temperament. However, did the singer do such a complex tuning in those days?
Since Music in Baroque era, the root or melodic line is clearer than Renaissance Music, then we can fairly easy to decide the basis of tuning to control the pitch. In the Music of Renaissance era, contrapuntal style is the main characteristic of the music and this characteristic often made the functionality of melodic lines between parts equal in harmonic point of view. Moreover, in those days, the singer only had his own part score when singing, that is why, it is hard to believe that the singer can control such a complex tuning.
In sacred music, we also have to think relationship between singer's temperament and those of organ's. It seems strange for me that the singer's temperament is different from the organ's temperament even if the work is a capella style.
Considering these things, we propose our recommending temperament in each work of sacred music in Medieval and Renaissance era we show below based on the keyboard temperament in those days.