When the が row goes nasal

What bidakuon is

Pronouncing the が row (が ぎ ぐ げ ご) nasally is called bidakuon (鼻濁音). The sound is close to the ng in English "singer".

Read かがみ (mirror) with bidakuon and it sounds like "ka-nga-mi" — the が comes out through the nose rather than the mouth.

It was traditional in the Tokyo dialect and eastern Japan generally, and it was written into NHK’s standard pronunciation guidelines for announcers.

Where it applies

• Not at the start of a word — the が in かがみ is nasal; the が in がっこう is not.
• The particle が — 私が (I, as subject) takes the nasal one.
• The number 五 inside a compound — the ご in じゅうご (15).

It is not used in loanwords, in sound-effect words, or when counting numbers distinctly. The ギ in ギター (guitar) is an ordinary ギ.

You do not need to learn it

Honestly, this pronunciation is fading fast. Younger speakers largely do not use it, and western Japan mostly never did.

NHK relaxed the guideline in the 2000s, and not using bidakuon is no longer treated as an error.

So there is no reason to drill it as a learner. It is worth knowing only so that the question "why does that が sound different?" has an answer when you watch older news footage or a period drama.

If you want to try it

English speakers already own this sound: it is the ng in "singer" — crucially not the "ng-g" of "finger".

So say かがみ as "ka-nga-mi" with the ng of "singer", kept very short, and you are close.

But as above, skipping it is entirely fine. Plain が is standard now.