pronunciation - The nasal allophones of /g/

In this this post's comments, Zhen Lin said that the rules surrounding the nasal allophones in compound words are 'complicated', but couldn't remember them. I'd like to know what these complex rules are.

Answer

Here is what I know. If, by "complex rules", you refer to more complex ones than these below, I wish one of the experts here would post an answer.

By the way, the nasal sound we are discussing here is called 「鼻濁音{びだくおん}」 in case someone did not know. "Nose-muddy-sound", literally. Since you know the word now, you can hear how it actually sounds on Youtube. It has quite a few videos on the subject.

The other sound, I do not even know what it is called. It is the "g" sound used in English words such as "game", "forget", "sugar", etc. I will call it the non-nasal here.

The Big Basic Rules

1. 
   

   Use the non-nasal when the ガ行{ぎょう} syllable comes at the beginning of a word.

   
   

   
   
   

   「がっこう」、「がんばる」、「ぎんこう」, etc.

   
   

   
   


2. 
   

   Use the nasal for the particle 「が」. No exceptions!

   
   


3. 
   

   Use the nasal for basically all non-word-starting ガ行{ぎょう} syllables. (Exceptions will be discussed below.)

   
   

   
   

   「にんげん」、「おんがく」、「にげる」, etc.

   
   
   

   
   

Exceptions

1. 
   

   Use the non-nasal for all of the ガ行 syllables in onomatopoeias.

   
   

   
   

   「ギリギリ」、「ゴロゴロ」、「ガリガリ」, etc.

   
   

   
   
   


2. 
   

   Use the non-nasal for ガ行 syllables in non-Sino loanwords.

   
   

   
   

   「ポイントゲッター」、「オルガン」、「エゴ」, etc.

   
   

   
   


3. 
   

   Use the non-nasal for number "5" (「五」).

   
   

   
   
   

   「25日{にち}」（にじゅうごにち）

   
   

   
   

   「5月(ごがつ)」 will truly test your ability as the 「ご」 is non-nasal while 「が」 is nasal.

   
   


4. 
   

   When a ガ行 syllable is preceded by the honorific 「お」, it is a non-nasal.

   
   

   
   

   「おげんき」、「おぐあい」, etc.

   
   

   
   



5. 
   

   Compound words can be rather complex when the latter parts start in ガ行 syllables because, unlike everything else we have discussed above, "personal judgement" is invloved.

   
   

   In 「音楽学校(おんがくがっこう)」, for instance, the first 「が」 is 100% nasal, but the second 「が」 is pronounced with a non-nasal by the majority of us native speakers (including professional announcers, voice actors, etc.). This is because the part 「学校」 in the second half of the compound word "feels" more like an independent word to many of us than like just a part of the longer word 「音楽学校」.

   
   


6. 
   

   When an originally カ行 syllable becomes a ガ行 syllable by rendaku, that ガ行 syllable is pronounced as a nasal.

   
   

   
   

   「飛行機雲（ひこうきぐも）」、「天然氷（てんねんごおり）」, etc.

   
   

   
   

There should be a couple of more, I think, but this is all I can recall right now.

Here is a good video about 鼻濁音 by the National Institutute for Japanese Language and Linguistics.

https://www.youtube.com/watch?v=amscTH7z3iM