||This article may be too technical for most readers to understand. (March 2014)|
|Indian classical music|
Shruti or sruti (pronounced śruti) is a Sanskrit term, which in the context of Indian music, is the smallest interval of pitch that the human ear can detect. It has been used in several contexts throughout the history of Indian music.
To know the real meaning of shruti, it is important to know the various contexts in which the term is used.
Ancient period: Grama system
Bharata Muni uses shruti to mean the interval between two notes such that the difference between them is perceptible. He formulates jatis, which are classes of melodic structures. These can be further grouped into two gramas—shadja-grama and madhyama-grama. The notes (svaras) are separated by intervals, as measured in shrutis.
The shadja-grama is given by the following division: Sa of four shrutis, Ri of three shrutis, Ga of two shrutis, Ma of four shrutis, Pa of four shrutis, Da of three shrutis and Ni of two shrutis. Bharata also describes an experiment to obtain the correct physical configuration of shruti in shadja grama, Sarana Chatushtai.
The madhyama-grama is the same, but the panchama (Pa) has to be diminished by one shruti. That is, the panchama of madhyama-grama is lower than that of shadja-grama by one shruti, according to Bharata. Shruti is only mentioned as a perceptual measure in the music of Bharata's time.
In both the gramas, Ri is three shrutis away from Sa – there are three perceptible intervals between Sa and Ri. The third of these is called trishruti rishabha (Ri). Likewise, the second interval is called dvishruti rishabha, and the first ekashruti rishabha.
Notes nine and 13 shrutis from each other are mutually samvādi (consonant). The notes that are at the distance of two and 20 shrutis are mutually vivādi (dissonant). The remaining ones, at the distance between 2 and 20 shrutis, are called anuvādi (assonant).
The shruti table below shows the mathematical ratios considered to correspond to the system described by Bharata and Dattila, along with the comparable notes in common Western 12-TET tuning and comparable notes in 53-TET tuning. The names of the 22 shrutis were provided by Śārñgadeva.
|Shrutis||12-TET Notes||53-TET Notes||Perfect FIFTHs|
The 53-TET approximation has a maximum error of 1.5%, while the perfect fifths approximation has a maximum error of 2%.
The table below shows the Harmonic scales into shruti:
|HARMONIC MULTIPLES = Normalized x n
(n = 2,3,4,5,6,8,9,10,12,15,16,18,19,20,24,25,27,30,32)
As is shown, the harmonics in scales of shruti are multiples of prime numbers 2, 3, 5 and 19. There are no multiples of 7, 11, 13, 17, 23, etc., just of 19. In reality it is not 19, but 19.2, because 19.2/32 = 3/5, which means that the harmonic 19.2 becomes the harmonic 3 and all of the harmonics multiplies up by 5.
Medieval period: Mela system
By the time Venkatamakhin formulated the melakarta ("mela") system, the grama system was no longer in use. Unlike the grama system, the mela system uses the same starting swara. It forms the scales by varying the intervals of the subsequent swaras, and does not specify a fixed interval for a swara in terms of shrutis. For example, the intervals of kakali-nishada and shuddha-madhyama vary depending on the dhaivata and the gandhara that precede them, respectively. The interval of kakali-nishada is of three different shruti values depending on whether shuddha, panca-sruti or shat-shruti-dhaivata preceded it. Thus shruti as a measure of interval is not fully employed in the mela system.
Modern period: Controversy
In current practice of Carnatic music, shruti has several meanings. It is used by musicians in several contexts. For instance, the Tamil term "Oru kattai sruti" means that the tonic is set to the pitch C or the first key. The Telugu term "Sruti chesuko (శ్రుతి చేసుకో)" is a way to correspond with the accompanying artists to tune their instruments.
In certain ragas, due to inflexions or gamakas on some of those 12 notes, listeners perceive a sharpened or flattened version of an existing note. Some scholars have attempted to fit such perceived new tones into the non-contextual Bharata's 22 shrutis, which lead to confusion and controversy. It was also wrongly attributed to Bharata, who proposed shruti in a completely different context.
Some scientific evidence shows that these intermediate tones perceived in the contemporary rendition of a raga do not hint at the existence of 22 shrutis. The number 22 is of no practical significance in the current performance of Carnatic and Hindustani music traditions, partly because different musicians use slightly different "shrutis" when performing the same raga. The phenomenon of intermediate tones is pursued as an active area of research in Indian Musicology, which says the number of perceptible intermediate tones may be less or more than 22. N. Ramanathan, a musicologist points this out and says that the idea of 22 shrutis is applicable only to the music system of Bharata's time.
An Indian monograph about shruti claims various opinions about the number (66, 53) of shrutis. In recent times it seems that the number of shrutis is broadly agreed upon to be 22. Recognizing the controversy over the number and the exact ratios of shruti intervals, it also says that not all shruti intervals are equal and known as pramana shruti (22%), nyuna shruti (70% cents) and purana shruti (90%). Еach shruti may be approximated in 53EDO system.
Ancient treatises on Indian classical music and performing arts
- Natya Shastra by Bharata
- Dattilam by Dattila
- Brihaddeshi by Matanga
- Abhinavabharati - Abhinava Gupta's commentary on Natya Shastra
- Sangita Ratnakara by Sarangadeva
- Bakshi, Haresh. 101 Raga-s for the 21st Century and Beyond: A Music Lover's Guide to Hindustani Music.
- Ramanathan, N. Sruti in Ancient, Medieval and Modern Contexts, an article from musicresearch.in
- Krishnaswamy A. Inflexions and Microtonality in South Indian Classical Music. Frontiers of Research on Speech and Music, 2004.
- Krishnaswamy A. On the twelve basic intervals in South Indian classical music. AUDIO ENGINEERING SOCIETY. 2003
- Datta, A. K.; Sengupta, R.; Dey, N.; Nag, D (2006). Experimental Analysis of Shrutis from Performances in Hindustani Music. Kolkata, India: SRD ITC SRA. p. 19. ISBN 81-903818-0-6.
- Ibidem. p. 28.
- Khramov, Mykhaylo (December 2011). "On Amount of Notes in Octave" (PDF). Ninaad, Journal of the ITC-SRA (Kolkata, India) 25: 31–37. ISSN 0973-3787.