MPRO plays most pieces using Mean Tone Tuning.  Almost all instruments today are built to Equal Temperment -- a tuning system that has each of the 12-notes in the scale be in an equal ratio to each other.  This allows the instruments to play equally well in all keys.  However, in order to achieve this, the intervals of a third and a fifth are no longer "perfect" in Equal Temperment.  In Mean Tone Tuning, the thirds are perfect, which gives them a better sound and greater power.  Mean Tone was the tuning used in the Renaissance and Baroque periods, Equal Temperment not becoming accepted until the 19th century.  Note that Bach's The Well-Tempered Clavier was an attempt to popularize a well-tempered tuning system designed to solve the same problem. 

For more information on tunings and temperments, see the article
Pitch, Temperament & Scale by Brian Blood, of Dolmetsch, Inc.

Playing in Mean Tone Tuning on Modern Instruments

In order to pay modern Equal Temperment instruments in Mean Tone, the following procedure must be used by each player:


Lower all sharps
(F#, C#, etc.)



Raise all flats
(Bb, Eb, etc.)



Lower the notes
E and B



Raise the note F


Adapted from a paper by Frederic Palmer
February 1989