My dad, a retired scientist from ISRO and a connosieur of Indian classical music has a few observations about the similarities between Remote sensing and Indian classical music.
INDIAN CLASSICAL MUSIC AND REMOTE SENSING TECHNIQUE
-- Some similarity considerations.
Dr. P. N. PATHAK (Member, RIOAA)
Tel. – +91 79 26309972
Introduction
Through this strange-looking title, I want to share my views regarding
similarities between some concepts of Remote sensing technique and those of the Indian classical music. Before I joined Space Applications Center around 1980's, I had some knowledge and understanding of the Indian classical music. Later on, when I was introduced to the science of remote sensing, my mind was drawn to some similarities between these two different disciplines. This article attempts to present some results of this study. The present exercise is purely an academic work and nothing more. Because I believe that music which basically appeals to our aesthetic senses can never be compared with a scientific subject. Moreover, music is a manmade system of art whereas remote sensing technique is a science. Before we discuss the matter further, it would be necessary to introduce the basic concepts of the Indian classical music.
Indian classical music
What is generally known as the Indian classical music is a part of the manifold cultural heritage of India. Vedas, Upnishads, .Epics like Ramayana and Mahabharata and several mythologies refer to music, musicians and different musical instruments. Like all systems, classical music also has its own terminology, concepts and definitions. Swar-Nad or sound which is used in music is called Swar or note. There are seven basic Swars or notes. These are: Shadaj (Sa), Rishabh (Re), Gandhar (Ga), Madhyam (Ma), Pancham (Pa), Dhaivat (Dha) and Nishad (Ni). These seven notes make a Saptak or Shuddh swars,
– In Western music it is called octave.
The seven notes or swars are understood in classical music in the following way. Sa and Pa are fixed and have no variation, i.e. they do not vary from their positions. The remaining swars Re, Ga, Dha and Ni can be taken at a lower frequency and are called Komal. Thus, there are komal Re, Ga, Dha and Ni. In contrast to these, swar Ma can be taken at a higher frequency, which is called Tivra Ma. Hence, a Saptak has seven shuddha notes and added to these are four komal and one tivra note (swar). Thus, a saptak has actually twelve notes- seven shuddha notes, four komal and one tivra note. These are the basic alphabets of the Indian classical music. But just as learning the alphabets is not learning the language, the saptak as such does not tell us anything about the most important aspect of the Indian classical music, namely the Raag or the melody structure.
The Raag System
Indian classical music is essentially based on melody. In practical terms, this would mean that no swar is taken as an individual note but as related to another, either lower or upper note. A note or a group of notes when heard gives an impression of a melodious movement. The Raag system, put logically, is the outcome of this process. By convention, a Raag should satisfy the following norms.
(1) A Raag must have aaroh and avroh, i.e. ascending and descending notes.
(2) It should have a minimum of five notes in aaroh and avroh. Maximum number of notes can be nine.
(3) A Raag must have the steady notes Sa and Pa or alternatively, Sa and Ma.
(4) As pointed out above, a Raag must be a melodic structure; not a mathematical exercise. In simple language, a Raag must appeal to the aesthetic sense, it must entertain. This depends very largely on the melody created by the Raag; it also depends largely on the artist or the musician.
(5) Each Raag has been specified a certain time in a day, when it should be sung.
I.e. for example, early morning, afternoon or late night hours.. In addition, certain Raagas are seasonal, that is, either for rainy season or spring season. For example, the Raag Malhar is for rainy season and Basant is for the spring season.
Every Raag has the aaroh-avroh, which, when sung shows the unique signature of the Raag. In addition, there is a Pakad, a particular combination of different notes for every Raag; which also helps to give a unique distinction to the Raag. When a song or a lyric is added in the Raag, it gives one more dimension to the system.
In the actual singing or playing, every Raag reveals certain noticeable patterns and emphasis. In a Raag, a note may be emphasized relatively more, another note may take the second place. The note with the highest emphasis is called the Vadi and the note at the second place is called the Samvadi. These few terms form the basic grammar of the Raag. For example, in Raag Bhupali the notes are Sa, Re, Ga, Pa, Dha, Sa. Its typical description is as follows: The Raag Bhupali is Odav, Odav, i.e. it has five notes in Aaroh and five notes in Avroh. All notes are Shuddha, no Komal notes. Vadi note is Ga and Samvadi note is Dha. .The Madhyam (Ma) and the Nishad (Ni) notes are avoided. In musical description, these are called Varjya notes or forbidden notes.
In addition, there is a Taal or rhythm. But here we do not consider this aspect of the Indian music. It is important to understand that by reading books on Indian classical music, it is not possible to learn the music. It is only through learning under a musician or a Guru/ Ustad for a long time as well as regular Riaz (practice) for a long time, that it is possible to master the art of music.
Remote Sensing Technique
Remote sensing deals with the experimental observation of the electromagnetic radiation scattered/reflected or emitted by objects and features at or very near the earth's surface. In practical sense, an instrument (sensor) onboard an aircraft or a spacecraft detects the scattered/reflected radiation during daytime by different features on the earth in a number of spectral channels. The number of spectral channels depends on the different features on the earth which are required to be identified.
For agriculture and forestry a combination of visible and near- infrared channels is particularly important. An important tool for the examination of the results is obtained by plotting the reflectance for different spectral bands. It has been found that the reflectance by vegetation in the near- infrared channel is generally much higher than in other visible channels. This feature is called the spectral signature, which is extensively used for identifying different features on earth like, vegetation, land, water, ice etc In addition, visual photo-interpretation of the image is also used for the analysis.
Another method is the use of principal component analysis, which can help in deciding which spectral channels have maximum probability of occurrence. Together with this analysis it is also necessary to collect the ground truth information for verification of different features on the earth.
Similarities between the two disciplines
At the outset, it is important to note that Remote sensing technique is based on the electromagnetic spectrum, whereas music is based on sound waves of different audible frequencies. Of course, both are waves, but that point is not considered here.
Secondly, music is capable of appealing to our aesthetic senses, but remote sensing has no aesthetic appeal as such.
The most important concept in remote sensing is that of spectral signature which helps in the identification of the observed feature. In music, Aaroha-Avroha and Pakad are the most important concepts like spectral signature, which help in the identification of the Raag. Similarly, the Vadi and Samvadi notes are somewhat similar to the principal component analysis, which are useful for the identification of the Raag. In remote sensing, certain visible and near-IR spectral bands are used during daytime, because these are reflected/scattered by the features on the earth. However, a band near 4 micron should be avoided because the daytime reflectance and emission by the earth are nearly equal at this wavelength. This is similar to the Varjya note(s) in some Raag. Similarly, a band near 1.6 micron is for reflectance by snow during day and therefore cannot be used at nighttime. This may be compared to the daytime Raag. Like seasonal Raag, seasonal features of trees and vegetation on the earth as well as winter season for snow-cover on land are also used in remote sensing to distinguish certain features For the last few points, the author is thankful to Dr. Pranav Desai for the suggestion. The author would appreciate comments and suggestions from the readers.
References
(1) Pathak, H.N. Indian Classical Music (Article in English in the Gujarati book "Nadbrahma Ni Samipe", published by Rannade Prakashan, Ahmedabad, 2001)
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(2) Pisharoti, P. R. Introduction to Optical Remote Sensing ( Indian
Space Research Organization), Bangalore, 1977.
Apoorva Pathak
+973 36796998
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