Tuning is a central but seldom discussed part of the early-music movement. There is little doubt that music of the early Baroque was played with a different system of tuning (or ''temperament'') than is common today. The difference it makes to the music can be hard to pin down, but musicians agree that even to listeners who can't describe it, the harmonies will sound unfamiliar if not outright strange.
Baroque zealots tend to disdain modern, or ''equal,'' temperament, suggesting that every note is ''equally out of tune.'' Their ears have become accustomed to unequal temperaments. The challenge is to convince fellow musicians to learn to use and appreciate those tuning systems. Audiences, too, sometimes show resistance.
In the early 17th century the ideal was to have the third, an important note in a major chord, sound acoustically ''pure.'' This was called ''mean tone'' temperament. To modern ears, ''pure'' often translates as ''out of tune,'' when a chord is compared with its counterpart in equal temperament. On the other hand, once the ear is used to the pure thirds of mean tone, that major chord gives a wonderful sense of repose. At the same time, other mean-tone chords sound wildly dissonant, giving the music great energy. Neither effect is possible in equal temperament, which has no pure intervals at all.
Musicians who have explored historical temperaments come to feel strongly about them. As a member of the Baroque trio Romanesca, the English violinist Andrew Manze recently astounded Americans with his inspired playing of the 17th-century ''stylus phantasticus'' repertory. Mr. Manze's mastery of the nuances of tuning was obvious in the group's New York debut concert at Weill Recital Hall.
Mr. Manze finds it natural to play in Baroque temperaments. ''On a violin, if you put your fingers on the neck without effort, it's mean tone,'' he said. ''The fingers end up being farther apart than we're usually trained for.''
Surely the most famous mention of a musical ''temperament'' is in the title of Bach's ''Well-Tempered Clavier.'' The late 17th and the 18th centuries produced a variety of temperaments that stretched the thirds and fifths of chords to varying degrees, approaching the idea of modern equal temperament. Even in Bach's day, ''well tempered'' was different from ''equal.''
''On a well-tempered keyboard, you could play in all keys more or less acceptably,'' said Raymond Erickson, a musicologist and harpsichordist at Queens College and the director of the Aston Magna Academy. ''But certain chords would still be more racy or ripe than others.''
Mean-tone becomes problematic in larger ensembles. ''For orchestral music, you have to be careful,'' said Stephen Hammer, a Baroque oboist and the artistic director of the New York Collegium. ''I don't think equal temperament is so bad. It needs to sound in tune above everything else. Thinking in a temperament limits how in-tune you can play.''
The oboe does not have fixed pitches, like a harpsichord's strings, so it is not restricted to a particular temperament. The violin and other fretless string instruments are also free of such limitations except in the way their open strings are tuned. ''Temperament is very important,'' Mr. Manze said. ''For the violin there's no pattern to follow unless there's one in your own mind.''
With fretted string instruments, like the guitar, lute and theorbo, and the various viols, the design of the instrument changes the rules. Because each fret goes all the way across the fingerboard, it creates equal intervals on each string. So equal temperament was advocated for tuning lute strings as early as the 16th century. Yet lutenists have learned tricks to ''temper'' their instruments in ensembles, like tying pieces of gut just above the fret, or attaching bits of toothpick to the fingerboard.
Keyboard instruments have their own special issues. On a modern piano, for example, there is one black key between the white keys D and E. That black key is called both D sharp and E flat. On a harpsichord in mean tone, D sharp and E flat are separate pitches, a fifth of a tone apart. A key tuned as E flat cannot be used for D sharp.
During the mid-15th century in Italy, composers and players experimented with chromatic notes. It occurred to someone to make two small keys between D and E, so that the keyboardist could play either D sharp or E flat. And so the split-key organ and harpsichord were born.
The organ came first and was specifically designed to accompany singers in church. Split keys offered the great advantage of making every major and minor chord sound pure, avoiding the unhappy compromise of equal temperament.
CHRISTOPHER STEMBRIDGE, a keyboardist and musicologist at the School of Church Music in
Brescia, Italy, and an expert in Italian music of the late Renaissance and early Baroque,
owns an instrument called a ''cimbalo cromatico,'' or chromatic harpsichord. It has 19
notes per octave, allowing for every distinct natural, sharp and flat note. Such
instruments existed during the 17th century, in Italy and elsewhere.
The most extreme split-key instruments, called ''archicembalos,'' had 28, 31, even 36 keys per octave: obviously, more than two keys for each piano black key. ''It becomes very illogical to play,'' said Mr. Stembridge, who has tried to play a 1606 instrument with 31 notes per octave. ''I cannot imagine that anyone played fluently on this.''
Mr. Stembridge finds that his 19-note cimbalo cromatico poses no real problems for the player accustomed to ordinary mean-tone harpsichords. For each split key, the sharp or flat usually found in mean tone is at the front. The player reaches to the back of the key to find the less-used chromatic note.
Like split-key organs, the cimbalo cromatico was originally intended to accompany singers. But some composers and theorists of the late 16th and early 17th centuries wrote pieces specifically to show off its unusual capabilities. These composers, like Ascanio Mayone and Giovanni Maria Trabaci, are not exactly household names.
When Mr. Stembridge plays in the United States, he uses a cimbalo cromatico built for him by Willard Martin, a harpsichord maker in Bethlehem, Pa. Mr. Martin has a special interest in the chromatic harpsichord, which reaches beyond the obvious issues of temperament.
The 16th century produced a flowering of neo-Platonic mysticism among the European aristocracy. One manifestation was an attempt to equate musical notes with visual colors.
Mr. Martin is interested in the 16th-century painter Giuseppe Arcimboldo. In a treatise from 1590, Mr. Martin explained, ''Arcimboldo presented a formula with which he had converted paintings into pieces of music.'' In that treatise he uses the word ''gravicembalo'' to describe the instrument in the court of Prague on which he made such a conversion. But Mr. Martin believes that it was some kind of cimbalo cromatico. According to court inventories, there was one in Prague at the time.
Unfortunately, Arcimboldo did not disclose which paintings he converted. As he was writing the treatise, he would have been painting the famous portrait of Rudolf II of Prague in fruits and vegetables.
''The neo-Platonic idea that tone and color can be unified was like an alchemic article of faith,'' Mr. Martin said. ''It's like trying to turn lead into gold. They believed it could be done but did not know how.''
Another, later, music-loving painter, Domenichino, made reference to the relationship of music to color in surviving letters. Mr. Martin is exploring the possibilities of this musical alchemy in collaboration with Thomas D. Kaufmann of the art department at Princeton University.
There is no question that the high-culture fashions of the late 16th and early 17th centuries were influenced by classical antiquity. Many experiments with music were aimed at recreating the sort of intense emotional response Aristotle described in his writings about poetry and rhetoric.
The cimbalo cromatico fits into this experimental movement. Its microtonal capabilities certainly intensify the rhetorical impact of the music. Mr. Stembridge recently demonstrated Mr. Martin's instrument to a gathering of music scholars, composers and performers in New York. Hearing so many pure intervals was disorienting. It brought out obvious physical and psychological reactions in listeners.
During a brief setting of the Kyrie by Ascanio Mayone, audience members were so alarmed at the bizarre sound that they began to giggle nervously. ''You're not supposed to be laughing,'' Mr. Stembridge said from the harpsichord. ''You're supposed to be praying.''
Mean-tone temperament is essential to unlock the emotional charge embedded in much early Baroque music. ''All the music written for the piano has missed out on the opportunity for this sort of expression,'' Mr. Manze said. ''Imagine what Liszt would have done with mean-tone.''
Even without questions of temperament, Baroque tuning would be a matter of controversy. Another essential issue keeps the pegs cranking up and down: pitch frequency.
Since the 1930's, pitch has been more or less universally standardized for Western art music. Today the A above middle C sounds at 440 vibrations per second. But during the Baroque, a baffling array of pitch standards were used for different instruments. From city to city, that A might sound at all sorts of pitches, from what the modern ear hears as an F above middle C, up to the modern high C.
Opinions about pitch vary widely among musicians determined to be historically accurate. Gwendolyn Toth, a harpsichordist and the director of the New York-based ensemble Artek, does her utmost to use the historically accurate pitch for any given piece. ''If you know something was at a high pitch and you change it to low pitch,'' she explained, ''to me it's the same thing as saying, 'Well, the composer wrote these 16th notes, but let's change them to these other notes.' ''
Mr. Martin agrees that pitch is a part of the music. He recently made a harpsichord at a remarkably low pitch, reflecting the overwhelming evidence for such a standard in Paris at the time of Louis Couperin.
''If you play Couperin at A = 345, which is a major third below 440, you can play slower and articulate differently,'' he said. ''The instrument teaches the musician a lot about the music.''
AS a performer, Mr. Stembridge sees the issue in another light. ''I don't think there's anything sacrosanct about pitch,'' he said. ''I see nothing wrong in playing music at whatever pitch makes musical sense and makes an instrument sing.''
At the opposite extreme from Couperin is Claudio Monteverdi, whose music is thought to have been originally played at a very high pitch. ''A lot of violinists are not happy about that,'' Mr. Stembridge said. ''I don't see any merit in trying to be authentic in a case where the musicians are uncomfortable.''
Enter the fearless Mr. Manze, known for his use of scordatura, a technique in which the violin strings are purposefully tuned at the ''wrong'' pitch to achieve particular effects. ''I think a lot of violinists are awfully precious about pitch, worrying that it will harm their instruments,'' Mr. Manze said. ''But I rather enjoy the danger of it.''
Yet on the subject of historical pitch frequencies, Mr. Manze is less enthralled. ''It has always left me rather cold,'' he said. ''The violin was designed to be played at all sorts of pitches. You just have to slot your brain into the right pitch, then you're fine.''
The pursuit of historical accuracy can be impeded by economics. Ms. Toth and her husband, Dongsok Shin, also a harpsichordist, together own nine instruments. ''When I first started playing, I thought I'd buy one French harpsichord,'' Mr. Shin said. ''But the more seriously you get into it, the more you realize that the regional differences between instruments are important.''
The physical environment can also wreak havoc on the best intentions. At a recent Artek concert at the Church of the Resurrection in Manhattan, the onstage tuning took so much time that the musicians nervously joked with the audience. ''We couldn't tune in the sacristy, because it was too cold, so everyone had to go out and tune with me,'' Ms. Toth said. ''The practicality is almost insurmountable.''
Mr. Shin has run into other practical troubles lately. ''I just did a concert at low French pitch,'' he said. ''But the three string players all had to go to the shop and have their sound posts adjusted for this concert. One of the violinists was playing other things. He had to borrow a violin so he wouldn't have to tune his instrument up and down.''
Not suprisingly, some musicians balk at such inconveniences. Part of their resistance may be caused by a lack of familiarity with Baroque practice. Playing on period instruments in period styles is not an everyday part of modern musical training.
Mr. Erickson, the harpsichordist and musicologist, teaches Baroque performance practice to doctoral students at the City University of New York, but even in that setting, practicalities limit him.
''Tuning is not one of my primary concerns in teaching, because the students here all play modern instruments,'' he said. ''They are used to playing in equal temperament. You can't just pick up every couple of weeks and decide you're going to play in mean tone. So I concentrate on those things, like bowing and fingering, that I think they can put immediately into their playing.''
All this fuss over pitch and temperaments may strike some as a tempest in a very arcane sort of teacup. Yet Baroque musicians and serious listeners find these issues of central importance. As Mr. Stembridge said, when asked why he commits such energy to his study of split-key instruments: ''No one would ever ask why the Metropolitan Museum of Art was restoring a great painting to its original colors. What I'm doing is the same thing.''