In my nine years of living in monasteries, I’ve lived in three types of Theravada monastery/hermitage so far:
- Ajahn Chah Branch Thai forest monasteries/hermitages
- Ajahn Chah-affiliated Thai forest monasteries/hermitages
- Mahamevnawa Sri Lankan monasteries
There was about a 10% overlap in chants commonly done, when comparing 1. and 2.
There was about a 2% overlap in chants commonly done, when comparing 3. with both 1. and 2.
Why such a low correlation? Because many (I’d say over half) of all the chants, which we would call “Pali Chants”, might be more accurately described as “Commentarial Avanti/Magadhi Chants”, meaning they are in the same ancient colloquial language (that the original Pali Canon were memorized in), but you do not find them anywhere in the Canonical texts. They are much, much later works, which have sort of snuck in to common usage, and have gained a seemingly centuries-old aura of authenticity, because they sound quite indistinguishable from Canonical Avanti/Magadhi chants.
For example, when you look in my tradition’s “A Bhikkhu Manual - Essential Chants”, any chant which says “[THAI]” or “[TRAD.]” at the bottom is one of these “Commentarial Avanti/Magadhi Chants.” You can see a chart of these square-bracketed abbreviations on page 4 of my tradition’s “Bhikkhu Manual -Vinaya Notes”, (which helps to decode which of these chants came from where).
You’ll probably also be surprised to learn that “[TRAD.]” is effectively equivalent to “authored by King Mongkut, former King of Thailand.” Yes indeed, he personally composed several of the chants we commonly do in our tradition, such as the “Yo cakkhumā” and “Bāhuṃ sahassam”. Interestingly, the “Bāhuṃ sahassam” has spread to Sri Lanka, now being a rather popular chant, although they would very rarely know its origin.
Having said all this, there are some very common chants done across all traditions, and I agree memorizing those is a great idea (such as the Mangala Sutta, Ratana Sutta, and Dhajagga Paritta).
Also interesting is that there are several chants in several Canonical suttas, where the Buddha explicitly instructed the monks to memorize and chant them, but these Canonical chants have since totally slipped out of common currency, and even the chanting books (having been effectively replaced with “Commentarial Chants”).
For example, from the “Pāsādika Sutta: The Delightful Discourse” in the Digha Nikaya:
'Therefore, Cunda, all you to whom I have taught these truths that I have realised by super-knowledge, should come together and recite them, setting meaning beside meaning and expression beside expression, without dissension, in order that this holy life may continue and be established for a long time for the profit and happiness of the many out of compassion for the world and for the benefit, profit and happiness of devas and humans. And what are the things that you should recite together?
the four foundations of mindfulness,
the four right efforts,
the four roads to power,
the five spiritual faculties,
the five mental powers,
the seven factors of enlightenment,
the Noble Eightfold Path.
These are the things you should recite together.
See it in full here: http://redzambala.com/digha-nikaya/pasadika-sutta-the-delightful-discourse.html
Note how the subject matter quoted above contains “lists of Dhamma”, which contain Buddhist wisdom in and of themselves. You’ll notice that today’s “Commentarial Chants” just tend to heap lofty praise on the Triple Gem, but are relatively scant on containing actual Buddhist wisdom.