An Octave (Saptak) and its type

Octave

In Indian classical music, an octave is called a Saptak (or Saptaka). 

The term comes from the Sanskrit word sapta, meaning "seven," as it refers to a complete series of the seven primary notes (swaras) from Sa to Ni. 

A saptak is the musical scale within which a raga is performed and a melody is created.

The relationship between notes in a saptak is not based on equal temperament like in Western music. 

Instead, it is a relative system where all other notes are defined in relation to the tonic note, or Sa. 

The frequency of the last note of a saptak (the higher Sa′) is exactly double the frequency of the first Sa.

Types of Saptak

In Hindustani classical music, three main types of saptaks are used to cover the typical range of a human voice or an instrument. 

These are the lower, middle, and upper octaves, which are all relative to each other.

1. Madhya Saptak (मध्य सप्तक) - The Middle Octave

• This is the central or "middle" octave and the most fundamental.

• It is the natural range of the human voice, where most singing and playing occurs.

• It is the reference point for the other two saptaks.

• In notation, the notes of the Madhya Saptak are written without any special symbol (e.g., Sa,Re,Ga,Ma,Pa,Dha,Ni).

2. Mandra Saptak (मंद्र सप्तक) - The Lower Octave

• This is the octave below the Madhya Saptak.

• The frequency of its notes is half that of the corresponding notes in the Madhya Saptak.

• Singing or playing in this octave produces a deep, solemn, and resonant sound, often referred to as the "chest voice."

• In notation, notes in the Mandra Saptak are indicated with a dot below the note (e.g., Sa.,Re.,Ga.,Ma.,Pa.,Dha.,Ni.).

3. Taar Saptak (तार सप्तक) - The Upper Octave

• This is the octave above the Madhya Saptak.

• The frequency of its notes is double that of the corresponding notes in the Madhya Saptak.

• Singing or playing in this octave produces a high-pitched, bright, and sharp sound, often associated with the "head voice."

• In notation, notes in the Taar Saptak are indicated with a dot above the note (e.g., Sa′,Re′,Ga′,Ma′,Pa′,Dha′,Ni′).

A proficient musician, whether a vocalist or an instrumentalist, is expected to have mastery over all three saptaks, which allows them to explore the full range and emotional depth of a raga. 

In some cases, a musician may even venture into the Ati Mandra (lower than Mandra) and Ati Taar (higher than Taar) saptaks, though these are used less frequently.