Differences of 伴う and 同伴する

Question

I'm trying to understand the nuanced differences between 伴う and 同伴する.

My research (Weblio:伴う, Weblio:同伴) has led me to believe that:

同伴{どうはん}する means "a person accompanies another person", and not much outside that scope.

伴{ともな}う is the more general "to accompany, to follow along with" which may be used to talk about anything, such as wind accompanying a storm, or one problem accompanying another.

So, my questions are as follows:

1. Are the above assumptions correct? Are there any other nuances worth pointing out?
2. Does 同伴する refer to one person accompanying another exclusively, or can it be anything that accompanies a person? (ex: An aura of depression follows him wherever he goes.)
3. Is there any case where 伴う can not be used to mean "to accompany"? (Note: I'm asking for patently wrong cases here, not cases where 同伴する or some other word might be better.)

Answer 1

1. Are the above assumptions correct? Are there any other nuances worth pointing out?

   Almost correct, but one important thing is that the verbs are two-faceted words.

   • A が B に同伴する／伴う → A accompanies B
   • A が B を同伴する／伴う → A is accompanied by B

2. Does 同伴する refer to one person accompanying another exclusively, or can it be anything that accompanies a person? (ex: An aura of depression follows him wherever he goes.)

   Yes, people only, accompanying or accompanied by another. However, compounds such as 同伴者 usually only mean "accompanying person".

3. Is there any case where 伴う can not be used to mean "to accompany"? (Note: I'm asking for patently wrong cases here, not cases where 同伴する or some other word might be better.)

   First, accompany in music context ("to perform another part") is another word in Japanese: 伴奏【ばんそう】する (cf. 伴奏 accompaniment).

   Second, 伴う is not usable when you put A and B together.

   accompanied their advice with a warning (Merriam-Webster)
   → 警告に助言を添える、助言とともに警告する (though I think this situation can be handled by a single word, 忠告する)

   The word is also inappropriate when the subject doesn't change or make any move.

   the pictures that accompany the text (again Merriam-Webster)
   → 文章に添えられた絵／写真、文章に付随する絵／写真

   cf. the replacement of pictures that accompanies the text revision
   → 本文の改訂に伴う絵／写真の差し替え、本文の改訂に付随する絵／写真の差し替え