But how often does anger mask something else?
So maybe it's context dependent? Like fight/flight, vs feel disappointed because your toddler sister knocked down your magnatile tower...
I wouldn't necessarily use the concept of 'mask' (but, hey, it might apply sometimes) but I think I know what you are referring to. For instance, it's plenty common for people to initially feel FEAR (due to some automatic cognitive processing, e.g., due to automatic thoughts, beliefs, or schemas operating in the situation) and this to immediately be followed by ANGER. The same for other emotions such as frustration/embarrassment leading to ANGER, or even sadness (negative self-referent thoughts) leading to ANGER. For guys (maybe even more often military folks), anger is certainly a more 'acceptable' emotion to display (so there's a cultural reinforcement history at play). So there are many 'final common pathways' to the end state of anger. I just see it as a 'chain' of interconnected cognitive-emotional-behavioral phenomena...for example,
Parent sees kid run out into a busy highway; initially thinks 'My kid's gonna get killed' (which may actually be a rational thought at that point), feels terror; once the kid is safe, parent may have negative self-referent thoughts, 'I'm a bad parent, I'm awful, my child almost got killed because I wasn't watching them close enough,'; followed by negative other-referent (the child) thoughts such as, 'you never listen to me, you're stupid,' leading to anger and maybe yelling at the child; then maybe another negative self-referent thought, 'I'm a bad mother, I made my child cry.'
The most fascinating patterns I've seen in terms of situations that evoke anger in PTSD patients undergoing cognitive processing therapy (or other forms of CBT) is when they are particularly angered by other people engaging in behavior that is similar to their own negative self-referent beliefs (stuck points, particularly assimilated stuck points associated with their original trauma). For instance, if a veteran's original trauma were a combat situation where they blamed themselves for being 'ignorant' about a situation and they had guilt over their 'ignorance' getting their men killed, then I've observed that the most rage that they feel are in situations where they characterize other's behavior as reflecting their 'ignorance.' Yeah, I know that there's the classic 'projection' concept (and it may hold some weight), but you could also conceptualize things as chains of cognitive-emotional-behavioral interconnected phenomena as well, I suppose.