The pitch accent of Vedic Sanskrit, or Vedic accent for brevity, is traditionally divided by Sanskrit grammarians into three qualities, udātta "raised" (acute accent, high pitch), anudātta "not raised" (grave accent, low pitch) and svarita "sounded" (circumflex, high falling pitch).
In Vedic Sanskrit, most of the words have one accented syllable which is traditionally called udātta ("raised") and written with an acute mark ⟨◌́⟩ in the transcription. The position of that accent in inherited words generally reflects the position of Proto-Indo-European accent, which means it was free; i.e. not phonologically predictable from the shape of the word. Some words (finite verbs of main clauses, vocatives that do not occur sentence-initially, certain pronouns and particles) do not have an accented syllable, and only consist of unaccented syllables.
Unaccented syllables are called anudātta ("not raised") and are not marked in the transcription. Phonetically, accented Rigvedic syllable was characterized by height (rather than prominence) as a "high tone", immediately falling in the next syllable. This falling tone in the post-tonic syllable is called svarita ("sounded"). For example, in the first pada of the Rigveda, the transliteration
means that the eight syllables have an intonation of
- A-U-S-A-A-U-S-A (where A=anudātta, U=udātta, S=svarita),
īḷe is a finite verb and thus has no udātta, but its first syllable is svarita because the previous syllable is udātta. Vedic meter is independent of Vedic accent and exclusively determined by syllable weight, so that metrically, the pada reads as
- -.--.-.x (viz., the second half-pada is iambic).
In the period when Vedas were composed, svarita was not phonologically relevant. However, due to linguistic changes in oral transmission of the samhita before it was written down, mostly due to the loss of syllabicity of high vowels when followed by a vowel, this tone has become relevant and is called an independent svarita. In transcription it is written as a grave mark ⟨◌̀⟩. Such svarita may follow an anudātta. For example in RV 1.10.8c,
- jéṣaḥ súvarvatīr apá
- jéṣaḥ svàrvatīr apá
Independent svarita is caused by sandhi of adjacent vowels. There are four variants of it:-
- jātya (= "innate") (due to changes within a word, as in kvà for kúa, as in the example above (u becomes v before a vowel)
- kṣaipra (= "caused by quickness") (u becoming v or i becoming y where two words meet, as in vy-ā̂pta for ví-āpta) (i becomes y before a vowel)
- praśliṣṭa (= "coalescence") (vowel contraction where two words meet, as in divī̂va for diví-iva)
- abhinihita (= "close contact") (prodelision with avagraha where two words meet, as in té-'bruvan for té-abruvan).
In Latin script transcription, udātta is marked with an acute accent, independent svarita is marked with a grave accent, and other syllables are not marked with accent.
- svarita is marked with a small upright stroke above a syllable: ◌॑ (Unicode: U+0951)
- anudātta is marked:
- If it is next before an udātta or an independent svarita, it is marked with a horizontal line below the syllable: ◌॒ (Unicode: U+0952)
- If the first syllable in a pada is anudātta, that syllable and all following syllables which are anudātta are marked with the horizontal line, up to and not including the first syllable which is not an anudātta.
- If an independent svarita syllable is next before an udātta syllable, instead of putting the anudātta mark and the svarita mark on the same syllable, a numeral 1 (१) (if the svarita vowel is short) or a numeral 3 (३) (if the svarita vowel is long) is written between the syllables in question, and the numeral bears both the svarita mark and the anudātta mark. Hence we see अ॒प्सु (apsú) + अ॒न्तः (antáḥ) → अ॒प्स्व१॒॑न्तः (apsvà(1)ntáḥ), or क्व॑ (kvà) + इ॒दानीं॑ (idā́nīṃ) → क्वे३॒॑दानीं॑ (kvè(3)dā́nīṃ) 
- Other syllables are unmarked.
- A Vedic Grammar for Students, by Arthur Anthony Macdonnell, publ. Motilal Banarsidass