NG Sound

/ŋ/ is a nasal consonant sound made by touching the tongue against the velum. The same place as /k/ and /g/:

When you pronounce /ŋ/, noise escapes through the nose. Just as it does with /m/ and /n/.

The /ŋ/ phoneme does not appear in the English alphabet. But it’s easy to spot because it’s normally one of:

n + g = THING  /θɪŋ/
n + k = BANK /baŋk/
n + c = ZINC /zɪŋk/

/ŋ/ in Connected Speech

If /n/ ends a word such as IN and the next word begins with /k/, the words will join and the /n/ turns into /ŋ/:

SEPARATELY: /ɪn ˈkɛnjə/
JOINED: /ɪŋˈkɛnjə/

The same occurs with /g/:

/ðɛn ˈgəʊ/
/ðɛŋˈgəʊ/

This process is called ASSIMILATION.

/ŋ/ in Accents

Words that end in NG such as:

long /lɒŋ/
hang /haŋ/
thing /θɪŋ/

are pronounced without the final /g/ in most accents of the UK and Ireland, though you will hear the /g/ in areas of the Midlands and North of England:

/lɒŋg/
/haŋg/
/rɪŋg/

-ing Endings

In words such as:

PLAYING
WORKING

the G is removed in most accents (throughout the UK and Ireland):

PLAYIN’
WORKIN’

pronounced with /ɪn/ NOT /ɪŋ/.

In Received Pronunciation (RP) / General British (GB), the endings are pronounced /ɪŋ/ and this is the pronunciation you’ll find in British dictionaries.

But some people pronounce them /ɪn/ in informal situations and /ɪŋ/ in formal situations.