By Jahangir M. Abadi, Ph. D
Anyone who has tried to play a Persian melody on a fix-toned and chromatic-tuned Western instrument such as a guitar or piano will soon feel frustrated due to the lack of certain essential sounds. A comparison of two-fretted instruments, a setar and a guitar, illustrates the differences between the two musics and the reason for the inadequacy of Western instruments for playing the traditional music.
Although both guitar and setar recognize the principle of octave, there are major differences between the two instruments:
1) The guitar has thirteen notes and twelve intervals per octave while the setar has eighteen notes and seventeen intervals per octave.
2) The twelve intervals in the guitar, also known as semitones, increase in pitch at a constant rate of 100 cents per semitone, but the setar's incremental rate is not constant 1.
3) In spite of the fact that both instruments use eight-note scales, the guitar's choice is limited to eight out of possible twelve notes, compared to the setar's choice of eight out of seventeen notes.
4) There are major differences in the modal pattern of the two musics. In Western music, both the major and the minor modes are supported by the same scale: the tempered chromatic scale. In contrast with Western music, the traditional Persian music is divided into seven "Dastgahs", which subdivide into "Naghmehs" and further into "Gushehs", each with a distinct label (2). The entire Dastgah system, including its subdivisions, is supported by at least five distinct scales (or "gAm"), called "kook", each of which is named after the major Dastgah that it supports (3).
As noted above, the thirteen-note scale with twelve equal intervals, known as the chromatic scale, is the backbone of Western music. Although in recent years many Iranian musicians have exclusively used this scale in their performances, the contrast between Western and Iranian music remains unmistakable and the air of mysticism generated by the traditional music is difficult to duplicate by either the tempered scale or by the instruments primarily designed for that scale. Having said that, we should also recognize the pioneering work of some musicians who have used Western instruments to produce traditional music, e.g., the virtuoso wind instrumentalists who by their lip control produced so-called “quarter notes" or Ostad Ruhollah Khaleghi and his orchestration for a mixed assembly of traditional and Western instruments. For sure, among the innovative musicians, the piano-players have a distinguished place for their efforts to adapt a purely Western instrument like a piano to the traditional music.
Use of the piano for traditional music has a long history, going back for at least one hundred and twenty years. The early piano players taught themselves to add the necessary tones by re-tuning certain keys on the piano keyboard. This process, which is still being practiced, yields a non-tempered piano which supports only one or two Dastgah(s) at a given tonic. Due to the lack of exact standards and accurate measurements of sound frequency in the past, it is not possible to state with certainty the number of necessary modified scales, or "Kooks" (3), to cover the entire Persian music, but there is a general consensus that there are at least five "kooks” which cover the seven major Dastgahs as follows:
Kooks Supporting Dastgah(s)
modified scales
__________ __________________
Mahoor Mahoor and Rast-Panj-gah
Shoor Nava and Shoor ( Dashti, Abu-ata, Afshari and Bayat-zand)
Chahr-Gah Chahr-Gah
Sehgah Sehgah
Homayun Homayun (including: Esfahan and Shushtari)
Occasionally, musicians further modify the above Kooks in order to play more than one dastgah within each performance, e.g. Mahoor and Shoor or segah and afshari. This is an important added feature since it enables a musician to go from one dastgah to another and back to the original dastgah without interruption. This sequential performance is called "morakab navazi" which is often employed by the experienced musicians.
It should be obvious from the foregoing account that piano re-tuning becomes a necessary routine for a musician seeking a desired kook. Unfortunately, re-tuning a piano is a long and exacting process which requires sharp ears and a great deal of experience; for that reason a considerable length of time should be devoted to re-tuning before every performance. There are other undesirable consequences as well: piano strings are designed to bear a constant tension for chromatic tuning, and repeated re-tuning could damage either or both the tuning mechanism and tone quality. The late Ruhollah Khaleghi, one of the earliest musical pioneers, noted the inadequacy of the chromatic scale and suggested a twenty-four tone scale in his book "Nazari beh Musiqhi" which was first published in 1938. With the universal adoption of the chromatic scale and no prospect of modifying piano keyboards, our only remaining choice is to shorten and simplify the re-tuning proesss. Perhaps the idea had crossed the mind of the late Ostad Khaleghi but its implementation had to wait many years, for the future innovations in electronics to take shape. With the advent of digital micro-electronics, the use of a special digital code for music called MIDI (Musical Instrument Digital Interface) and very fast computers, all connected to a "dumb keyboard" called a controller, it is now possible to tackle the job of re-tuning in a few seconds, versus an hour or so. Before we leave this topic, let me add that I am aware of the controversy regarding the sound quality of acoustic piano vs. electronic piano. I have to leave that to your judgment, after having listened to the rendition of an expert Persian piano player, Mr. Ramin Zoufonoun on a Yamaha Keyboard PSR-550.
Any keyboard, including the one named above, is an assemblage of a very sophisticated computer and microelectronics plus a sound-generating device called a synthesizer which can output several hundred musical tones, simulating a variety of musical instruments. Besides the musical sounds, the keyboards with MIDI connection can transmit streams of digital codes which characterize the tone, its frequency, its duration and several other important parameters in a musical performance. The codes, being of a digital nature, can then be saved as MIDI files which are subject to further editions and correction like any other computer file. Furthermore, through the use of softwares called sequencers, one can combine several MIDI files (up to sixteen files ) with a variety of tones, creating a virtual orchestra (See: David Miles Huber. The MIDI Manual- A Practical Guide to MIDI in the Project Studio). A small historical diversion- Johan Sebastian Bach suggested the tempered scale in order to harmonize a variety of musical instruments. The Persians apparently saw no advantage to do so but now through the use of computers, we too can harmonize up to sixteen tones in any tempered or non-tempered scale.
One of the unique feature of the Yamaha keyboard PSR-550 is its
scale tuning software. This software enables a musician to adjust the pitch of any key, up to plus or minus 64 cents, from its tempered position which is initially set at zero. By adding to, or subtracting from the initial setting for a key, its frequency is increased or decreased and its two adjacent intervals are readjusted proportionately. In principle, the electronic re-tuning is similar to mechanical re-tuning, except that it is far more precise, has no adverse effect on the piano and the readjustment is made only to a single octave. Besides the scale tuning software, there is another more common software called microtuning which adjusts the frequency of the entire keyboard but not the individual keys. The scale tuning software, which is a must in retuning a keyboard, is only present in the more expensive models.
The table below graphically illustrates the procedure for converting the A-minor scale to a scale or to a kook, compatible for Shoor Dastgah :
A-minor (tempered)
Tones A B C D E F G A
Offsets 0 0 0 0 0 0 0 0
Intervals 200 100 200 200 100 200 200 (cents)
Shoor-A (non-tempered)
Tones A B C D Eb F G A
Offsets 0 -50 0 0 +50 0 0 0
Intervals 150 150 200 150 150 200 200 (cents)
As shown above, every interval in A-minor is either one hundred or two hundred cents, or in other words, one or two semitone(s). For changing the scale of A-minor to a scale for Shoor, we have to roughly readjust the first and second intervals from 200 and 100 cents to two 150 cents intervals. We do this by changing the setting of B from zero to minus-50. Through this subtraction we convert the note B to B-koron (B half-flat). We repeat the same process on the note Eb, this time by adding +50 cents which converts Eb to E-koron and modifies the fourth and fifth intervals to 150 cents each. E-koron is used for some Gushehs in Dastgahe Shoor and as an accidental note in Afshari and in Dashti. Notice that in this process the frequency of E remains the same as in the Western A-minor tempered scale. By doing so we have the choice of using Eb sometime, all the time or not at all, as the music requires. The above procedure yields only a rough approximation of shoor-A. A further fine tuning, by comparison with traditional music, preferably played by a traditional instrument, is essential in arriving at the final product.
Harmonizing a re-tuned keyboard with traditional instruments is difficult, because the instruments are seldom tuned to the international pitch (A=440 Hz). Although the micro-tuning program can accurately alter the keyboard's pitch, the keyboard itself reverts back to the tempered scale. By modifying the pitch-bend device, it can be used to closely match the tones from the traditional instruments and the keyboard.
Jahangir M. Abadi
[ میهمان گرامی برای مشاهده لینک ها نیاز به ثبت نام دارید]
11/15/2005
1- Cent is the scientific unit for measuring the intervals between two different sound frequencies, for example, the frequencies generated by the two different keys on the piano. Interval is calculated as follows:
Interval in cent = Log ( higher frequency in Hz / lower frequency in Hz ) X 4000
If the interval is one octave the above ratio is 2 and the calculated interval = Log (2) X 4000 = 0.3 X 4000 =1200 cents. Similarly, for one semitone interval in the tempered scale, the ratio is 1.0594 and the calculated interval = Log ( 1.0594) X 4000 = 0.025 X 4000 =100 cents.
For non-tempered scales the intervals must be individually calculated from the offsets placed in each scale. The old method of expressing intervals, in terms of "Pardeh" or its fractions (1/2, 1/4, 3/4 etc.), is not accurate enough for the electronic piano.
2- For a more comprehensive discussion of Dastgah, Naghmeh, Gusheh and other terminologies commonly used in Persian music see " The System of Persian Music" in " The Art of Persian Music", p 57. 3- The word " Kook" in Farsi may be used as a verb or as a noun. As a verb, it denotes the process of tuning an instrument, either by changing the tension on the string, or less commonly by repositioning a few frets. As a noun, it points to the pattern of notes in an octave, which is roughly equivalent to "mode" in English, e.g., minor mode or major mode. In the latter frame of reference, "Kook of Shoor" is the sequence of notes that accommodates "Dastgah of Shoor" or the "Kook of Segah", which corresponds to "Datgah of Segah". The musicians often have to re-tune their instruments upon a change of dastgah, even in the fretless instruments like the violin. Because of repeated tuning the Persian musicians develop a highly discriminating sense of tone to the extent that in common vernacular a carefree individual is referred to as "well tuned".
Bibliography:
Farhat, Hormoz. The Dastgah Concept in Persian Music. Cambridge: Cambridge University Press, 1990,
Jean During, Zia Mirabdolbaghi and Darush Farhat. The Art of Persian Music. Mage Publisher, 1991David Miles Huber. The MIDI Manual- A Practical Guide to MIDI in the Project Studio. Focal Press, 1999.
