The standard pronunciation of this is nèiróng. However, I often hear (and sometimes myself pronounce, especially when speaking quickly) it as nèiyǒng (perhaps closer to a neutral tone on yong). Is this part of a larger phenomenon? Are there any similar sound changes in other words, where the second character's consonant is "softened"?
I don't agree wpt's answer.
I'm a native speaker and most of people won't pronounce
nèiyǒng unless you speak very very very fast(this phenomenon will happen on many many Chinese words).
And for mandarin, it is considered as non-standard pronunciation, you should avoid such pronunciation in formal condition.
And in my hometown and many other places, people speak dialect will have such pronunciation. They can not pronounce retroflex correctly cause they have speak
r as other pronunciation for many years. Even they do know the correct pronunciation, the habit let them not pronounce
r. And this maybe also change some other characters' pronunciation.
At last, the pronunciation of
r could be many changes. For example, the
热's pronunciation is
rè. But in
Shaanxi dialect, it becomes
yè. But the mandarin's pronunciation must be
rè regardless of how dialect pronounce.
Yes, initials can be affected by what comes before and after them. One example is the secondary voicing that occurs when the normally voiceless stops of Mandarin come between two vowels; for example, 爸爸 baba, written in close IPA transcription, supposedly should be /paba/, rather than /papa/. The second bilabial stop comes between two vowels and as a result becomes voiced.
In your example, however, this does not seem to be the case. r- is one of the retroflex initials; to pronounce it as IPA /j/ means it has lost its retroflexion, so you are alternating between retroflex and non-retroflex. This is not a regular phonetic process in Mandarin. Instead, many guanhua dialects do not have the retroflex initials; these speakers learn them later, and are prone to drop them in a variety of situations.
This is also the case in the Mandarin spoken in Taiwan （台灣國語）, and I tend to drop retroflexion myself, especially if I am talking fast, as you describe. I don't think it really matters if you drop it occasionally, as long as you can still remember which words have r- and which words have y- to begin with.