There are two major Indian classical music traditions, Hindustani (North Indian) and Carnatic (South Indian). The link is focused on the former. I'd like to add some (general, not just rhythmic) notes on the latter.
1. Both derive from the Sāmaveda, and took their modern forms beginning from the 15th century CE. What would eventually become Hindustani music took on Persian and Arabic influences, whereas Carnatic music—as the name suggests—is mostly limited to South India and therefore relatively insulated from the cultural changes in the North, and is considered closer to ancient Indian music.
2. Perhaps the most important difference between Indian and Western classical music is that the former is relative, not absolute. The main artiste picks a comfortable śruti, or tonic: males typically choose B to D, solo instrumentalists typically tune their instruments to D - F, and female artistes choose F# to A (and an octave higher). This is just a rule of thumb; some instrumentalists (flautists, for instance) prefer C. Note that I refer to only the note; the precise frequency/octave is irrelevant insofar as defining śruti is concerned. Once the main artiste has selected their śruti, all other accompanying instruments are tuned to the same. This is why ICM notation is solfège-based, staff notation does not work for ICM, and why Indian classical musicians have a taṃbūrā (could be electronic, too) on stage.
3. The ICM solfège is called swara. There are seven of these, called sa, ri, ga, ma, pa, dha, ni, just like in the West (do-re-mi-fa-so-la-ti). Similarly, they expand to twelve when accounting for semitones.
4. The basic melodic framework for ICM is the rāga; loosely put, this defines a certain scale that a composition, or parts of a composition, or some improvisation is set to. rāgas also define the gamakas, or ornaments for their scales; this is fundamental to ICM. There exist notationally equal scales with and without gamaka, but they are considered completely different rāgas.
5. There are loose analogues between ICM rāgas and Western modes. For instance, the Ionian mode is equivalent to Śankarābharaṇaṃ in Carnatic music, or Bilāval in Hindustani music.
6. Carnatic music rāga classification has an interesting tree structure. There are 72 'roots', called mēḷakartā, which have a complete scale of 7 notes ascending, and 7 notes descending. Delete some notes, or reorder them, or introduce one or more notes from another scale, and you get a veritable sea of janya rāgas.
7. Carnatic music has a few classifications for its rhythmic patterns. The suladi sapta tāla system is most commonly taught to beginners. In this, there are three angas (or parts): laghu, dhrutam, and anudhrutam. laghus can have 3, 4, 5, 7, or 9 beats (or akṣara), called jātis. There are seven arrangements (ergo, sapta) of angas under this system, and with five jātis, there emerge 35 talas with different akṣara sums for each. The typical 8-akṣara rhythm (again, similar to Western music) is called ādi tāla, or catusra jāti triputa talā.
A couple more things I'd like to add - please correct me if I'm wrong (I'm a listener, not a practitioner).
One important thing about rāgas that differentiates them from western modes is that they typically come with notions of note ordering. That is, when playing an ascending melody, you may be encouraged to pick different notes than for a descending one. There are a couple of western modes that work in a similar way, but typically only for a single note, and these modes are not widely used.
Another distinction is that while rāgas are like western modes in that they are culturally identified with emotional states, in ICM the emotional states are generally thought of as temporal (time of day, time of year). One does not think of a particular rāga as "sad" or "happy", but rather (for example) associated with sunrise, or twilight, or the deepest part of winter.
Finally, it is important to note that harmony plays very little role in ICM, which has instead developed its ideas regarding melody to a degree substantially beyond western classical music (which has focused a great deal of effort on advancing the concepts and use of harmony). Listening to ICM live with an experienced audience, you may hear gasps as the lead performer swoops up and down melodic lines, in ways that you would never encounter in a western context. For ICM listeners, the choice to play three particular notes one after the other can be a source of intense joy (or, occasionally, intense irritation).
I am hope I am writing about these aspects correctly.
> you may be encouraged to pick different notes than for a descending one
Hmm, this is not entirely true. There are absolutely symmetric rāgas, and some of these are extremely popular: I mentioned Śankarābharaṇaṃ, but there are several others, like Kalyani (Lydian mode), Tōdi (Phrygian mode), or pentatonic scales like Mohanam, Hamsadhwani, Hindōḷaṃ, etc.
> in ICM the emotional states are generally thought of as temporal
Indeed. One might think minor scales are 'more sad' than major ones, but this doesn't translate well to Indian classical music.
> it is important to note that harmony plays very little role in ICM
Also true. Indian classical music has little theoretical and practical use of 'chords' in the Western sense, except perhaps the drone strings on the vīṇā.
I dont know much about all this, but I am surprised there is nk mention of quarter tones here - western music does not have them, but I hear quarter tone intervals alllll the time in indian music. Yet you indicate that there are the same number of notes in a scale- but it seems indian music has an extra "blue note" or passing tone that we do not have here in the west.
> I am surprised there is nk mention of quarter tones here
There is some debate about 22 śrutis[1][2]. I subscribe to this paragraph from the second link:
> Further, there seems to be no point in trying to interpret these positions in precise mathematical terms. Such measured values do not in anyway contribute to the understanding of music.
In addition to the above, the gamakas I mentioned are a good abstraction over quarter-tones. For most practising musicians, 12 notes + gamakas are enough to describe Indian classical music. I understand Western classical music is a little stricter with its theory, but Indian music is less so, given a stronger aural-oral tradition in India rather than the written word.
Finally, mine was an already-long comment on a Hacker News thread meant to give a rough overview of Carnatic music to a (possibly untrained) Western audience, and not a detailed, thought-out blog post or article about comparative music theory and musicology.
1. Both derive from the Sāmaveda, and took their modern forms beginning from the 15th century CE. What would eventually become Hindustani music took on Persian and Arabic influences, whereas Carnatic music—as the name suggests—is mostly limited to South India and therefore relatively insulated from the cultural changes in the North, and is considered closer to ancient Indian music.
2. Perhaps the most important difference between Indian and Western classical music is that the former is relative, not absolute. The main artiste picks a comfortable śruti, or tonic: males typically choose B to D, solo instrumentalists typically tune their instruments to D - F, and female artistes choose F# to A (and an octave higher). This is just a rule of thumb; some instrumentalists (flautists, for instance) prefer C. Note that I refer to only the note; the precise frequency/octave is irrelevant insofar as defining śruti is concerned. Once the main artiste has selected their śruti, all other accompanying instruments are tuned to the same. This is why ICM notation is solfège-based, staff notation does not work for ICM, and why Indian classical musicians have a taṃbūrā (could be electronic, too) on stage.
3. The ICM solfège is called swara. There are seven of these, called sa, ri, ga, ma, pa, dha, ni, just like in the West (do-re-mi-fa-so-la-ti). Similarly, they expand to twelve when accounting for semitones.
4. The basic melodic framework for ICM is the rāga; loosely put, this defines a certain scale that a composition, or parts of a composition, or some improvisation is set to. rāgas also define the gamakas, or ornaments for their scales; this is fundamental to ICM. There exist notationally equal scales with and without gamaka, but they are considered completely different rāgas.
5. There are loose analogues between ICM rāgas and Western modes. For instance, the Ionian mode is equivalent to Śankarābharaṇaṃ in Carnatic music, or Bilāval in Hindustani music.
6. Carnatic music rāga classification has an interesting tree structure. There are 72 'roots', called mēḷakartā, which have a complete scale of 7 notes ascending, and 7 notes descending. Delete some notes, or reorder them, or introduce one or more notes from another scale, and you get a veritable sea of janya rāgas.
7. Carnatic music has a few classifications for its rhythmic patterns. The suladi sapta tāla system is most commonly taught to beginners. In this, there are three angas (or parts): laghu, dhrutam, and anudhrutam. laghus can have 3, 4, 5, 7, or 9 beats (or akṣara), called jātis. There are seven arrangements (ergo, sapta) of angas under this system, and with five jātis, there emerge 35 talas with different akṣara sums for each. The typical 8-akṣara rhythm (again, similar to Western music) is called ādi tāla, or catusra jāti triputa talā.
Some exemplary Carnatic music:
Vocal: Ramakrishnan Murthy, ānanda naṭana prakāśam, Muttusvāmi Dīkṣitar, Kēdāram, Misra Cāpu tāla: https://www.youtube.com/watch?v=Eu-tFbGpoTQ
Violin solo: Charumathi Raghuraman: https://www.youtube.com/watch?v=lESyDHH_E7Q
Vīṇā solo: Ramana Balachandran: https://www.youtube.com/watch?v=SgW3j9OVpJo
Flute solo: J.B. Sruthi Sagar: https://www.youtube.com/watch?v=v6InFwzX8kk