乐 Le and Yue: When did they diverge?

Question

In the character 乐, it has two readings in Mandarin. In pinyin, yue4 and le4 (plus other readings I take are literary)

In other dialects too, there seem to be 2 distinct forms. In cantonese, lok and ngok. In Min Nan, lok and gak. Wiktionary actually lists 3 pronunciations for these dialects. This is even reflected in Japan and Koreas' loaned pronunciations.

There are clearly 2 distinct readings of this character. My question is at which point did these pronunciations begin to become distinct? Due to the loan into Japanese and Korean, I take it could be quite some distance back in time, but the reconstructed Old Chinese pronunciation has only one apparent form (albeit this may be a mistake).

Perhaps there is no clear answer, but the etymological history of when these readings diverged is my point of interest.

Answer 1

I did some research. Here is what I found:

1) 樂 first meant music instruments, pronounced 'ngok'（逆角切）. In Japanese, it is がく［楽］(gaku).

2) The meaning happy '悦/樂' first had the same pronunciation 樂 as in 音樂. This was probably the case in 战国 (周朝)，because according to《爾雅·釋詁》(written after BC 476), 悦: 樂也。

3) In 唐韵 （written in 732 AD, 樂 meaning happy is pronounced 'lok' (盧各切). So the pronunciation changed between 周 and 唐, which is a long time (~1000 years). To cut the time shorter, we can look at Japanese, which borrowed a lot of Chinese characters between the 3rd - 5th century. In Japanese, ［楽］meaning happy is pronounced らく [raku]. So we know the 'lok' sound formed before 500 AD.

The timeframes map into the distinction between Old Chinese and Middle Chinese. Old Chinese 上古汉语 was used until the 3rd century and Middle Chinese 中古汉语 starts from the 3rd century.

Using this terminology, we can say this distinction is in Middle Chinese but not Old Chinese.

Furthermore, Old Chinese is considered to be very regular -- characters with the same component sound the same, and one character has only one pronunciation.

Now I guess the problem is solved. It seems that mathematical abstractions can help in reasoning and discovery! :)

PS. there could be a small difference in Old Chinese that led to larger difference in Middle Chinese. Old Chinese had double consonants. Later, double consonants are systematically dropped, and some words had consonant A and some with B. According to 韵典网 (ytenx.org/dciangx/dzih/%E6%A8%82)，樂's Old Chinese pronunciation was /ŋraːwɢs/, or transliterated as "ngrawgs". It had double consonants ŋ and r, so some words became ŋok, some became lok (r and l are the same), and some became ŋaw. The two meanings music and happy might had slight differences in Old Chinese.

Answer 2

The real answer is, the pronunciations were always distinct. In OC, the root written as 樂 simultaneously represented a number of different inflected forms, among which are: [ŋrawk], [ŋrawk-s], [g-rawk] (Baxter), each with a different grammatical function. Due to a process that included many complex steps, some subsequent compounds ended up with the [ŋawk] ... [yào] form while others ended up with the [rawk] ... [lè] form.

Nowadays, many meanings are not always distinguishable and sometimes conflated, but as others have pointed out, in the literary readings of old texts where archaic readings are maintained (they are not arbitrary!), three distinct meanings can be identified:

1. The noun form that is part of today's compound 音[樂] (music), with the meaning of "concordance." Music is literally "sonic concordance."

2. The archaic, transitive verb form as in 獨[樂]樂，與人[樂]樂, with the meaning of "to concord with" or "to accord to."

3. The passive verb form that grammaticalized into today's verb "to be joyful" and its related substantive, with the original meaning of "to be in concord."