The Science of Music – Class 9 Arts Chapter 7 Notes & NCERT PDF

Class 9ArtsChapter 7NCERT book: Madhurima - Arts Class 9

Notes and a simple summary of Chapter 7 of the NCERT Class 9 Arts book, with the official chapter PDF, flashcards, an MCQ quiz and an AI tutor for your doubts.

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Chapter 7: The Science of Music (Music)

Introduction

Music is both an art and a science. We enjoy it for the emotions, entertainment and relaxation it gives, but we can also study it in depth. This chapter connects music to physics (how sound is made), biology (how the human voice works) and mathematics (patterns and LCM in rhythm).

Instruments are grouped into four categories: tata-vādya (string), suṣhira-vādya (wind), avanaddha-vādya (percussion, with membranes) and ghana-vādya (solid). Examples pictured include the chimṭā, flute, santoor and mṛidaṅgam.

Key Ideas

C.V. Raman and Indian drums

C.V. Raman (1888–1970), the Indian physicist and Nobel laureate, studied the sounds of the mṛidaṅgam and the tabla. He found that they produce a sustained, rich sound and can be tuned higher or lower. Their membranes vibrate in complex patterns because of the karaṇai / syāhī, the black patch at the centre made of iron/manganese powder, starch and water.

The science of sound

From the rubber-band instrument activity, sound is produced by a vibrating string, and it can be changed by:

Tightening or loosening the string, which raises or lowers the pitch.

Using a hollow box, which increases the loudness.

Changing the thickness or material of the string, which changes the quality of the sound.

Real instruments use the same principles. The tanpura, veena, violin and sitar have hollow bodies and tuning pegs.

Ancient Indian ideas of sound: Texts like the Nāṭyaśhāstra and Saṅgīta-ratnākara explain dhvani (sound), nāda (musical sound), śhruti (discernible intervals of sound) and svaras (notes).

Biology of the human voice

The voice is a musical instrument in our own body. It has three subsystems:

Air pressure system: the diaphragm, lungs and surrounding muscles. Your belly expands as you breathe in.

Vibratory system: the voice box (larynx) and vocal folds / vocal cords. Feel it by humming mmmm.

Resonating system: the throat, mouth and nasal cavities. Change the mouth shape to make aaaa, oooo, eeee.

Saint Thyagaraja described the vocal system in his kriti Śhobhillu Saptasvara:

Nābhi hṛit-kanṭha rasana nāsādulayaṅdu Śhobhillu saptasvara suṅdarula bhajiṁpave manasā

"O Mind! Praise the divine forms of the seven musical notes, which glow in the abdomen, heart, neck, tongue and nose."

Caring for the voice

Drink enough water so the vocal cords stay hydrated and vibrate efficiently.

Eat healthily. Oily or very acidic food can irritate the vocal cords, while fruits and vegetables boost immunity.

Speak at a moderate volume. Don't shout.

Daily warm-up routine (5–6 times each): deep breathing (activates lungs and diaphragm for long phrases), humming / Bhrāmarī prāṇāyāma (warms up the vocal cords, improves resonance), lip trills (relax the face, improve airflow) and sargam alaṅkāras like SGR, RMG, GPM… or SRGM, RGMP, GMPD… (flexibility and breath control).

Mathematics in tāla

Rhythm is built from phrases of akṣharas (counts):

1 = ta, 2 = taka, 3 = ta kita, 4 = tha ka di mi.

5 = 2 + 3 = taka takita.

6 = 3 + 3 = takita takita, or 2 + 2 + 2 = taka taka taka.

LCM in rhythm (Activity 7.6): one group recites ta kita (3) and another ta ka di mi (4). They clap together again after 12 beats. That's 4 cycles of 3 and 3 cycles of 4, because the LCM of 3 and 4 is 12.

Worked examples

Teen Tāla (16 beats) and Ektāla (12 beats): LCM(16, 12) = 48. Both complete full cycles together after 48 beats (3 cycles of Teen Tāla, 4 of Ektāla).

Jhaptāla (10 beats) and Kehervā (8 beats): LCM(10, 8) = 40 beats (4 cycles of Jhaptāla, 5 of Kehervā).

Activities in the Chapter

7.1 Stringed instrument model: stretch rubber bands over a tissue box, then pluck, tighten and change the thickness.

7.2 Connecting to instruments: observe the hollow body and tuning pegs of a tanpura, veena or violin.

7.3 Experiencing the vocal system: breathe, hum, then shape vowels.

7.4 Daily vocal warm-up routine.

7.5 Rhythmic phrases for 7, 8 and 9 akṣharas.

7.6 The coming together of rhythms (LCM).

Key Terms

Tata-vādya (तत वाद्य): string instruments

Suṣhira-vādya (सुषिर वाद्य): wind instruments

Avanaddha-vādya (अवनद्ध वाद्य): membrane percussion

Ghana-vādya (घन वाद्य): solid instruments

Pitch (तारत्व): how high or low a sound is

Resonance (अनुनाद): the enhancement of sound in a hollow space

Larynx (स्वरयंत्र): the voice box

Vocal cords (स्वर-तंतु): folds that vibrate to make voice

Diaphragm (मध्यपट): the breathing muscle below the lungs

Syāhī / Karaṇai (स्याही): the black patch on a drum membrane

Akṣhara (अक्षर): a rhythmic count

LCM (लघुत्तम समापवर्त्य): lowest common multiple

Connect to Your Life

Notice how guitar and sitar players tune their strings, why your voice gets tired after shouting at a match, and how two rhythms meet in folk drumming.

Common Mistakes

Saying a looser string gives a higher pitch. Tightening raises the pitch.

Thinking the hollow body changes the pitch. The book links it to loudness.

Believing C.V. Raman studied the veena. He studied the mṛidaṅgam and tabla.

Adding beats instead of finding the LCM when rhythms meet.

Let's Reflect

Design your own string instrument using the principles of sound. What would it look and sound like?

💡 Key Learning Points

✓Instruments fall into four categories: tata (string), suṣhira (wind), avanaddha (membrane percussion) and ghana (solid).
✓String tension controls pitch, a hollow body increases loudness, and string thickness or material changes sound quality.
✓The human voice uses three subsystems: air pressure, vibratory and resonating.
✓Healthy habits and a daily warm-up protect the voice.
✓Rhythm follows mathematical patterns; LCM tells us when different rhythmic cycles meet.

👨‍🏫 Teaching Tips

→Open each period with a recording from a different instrument category and ask students to classify it.
→Let pairs build the rubber-band box instrument and record changes in pitch and loudness.
→Bring a tanpura, veena or violin and demonstrate the tuning pegs carefully.
→Lead the three-step breathing, humming and vowel-shaping activity to feel each vocal subsystem.
→Run the daily vocal warm-up at the start of singing lessons.
→Have two groups recite takita and takadimi together and count claps to discover the LCM.
→Link to the Grade 9 Science chapter on sound waves (Chapter 10) for the vocal cords.

📋 Assessment Questions

Can the student explain how tension, a hollow body and thickness change a string's sound?
Can the student name the three vocal subsystems and the body parts in each?
Can the student describe a daily voice warm-up and voice-care habits?
Can the student compose rhythmic phrases of 5–9 akṣharas?
Can the student find when two tālas complete cycles together using LCM?

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