Is it possible someone unskilled in fighting may be able to get a one time move to disable an expert fighter, simply by coming up with a weird move that made them go wtf and lose concentration? Something like bringing the fight to the next room and on entrance someone else clangs a cymbal in the expert’s ear to make them wince and let go and subsequent clangs smashes the guy’s head in the middle.
Taking this one piece at a time, it’s possible someone with no combat experience could get the drop on an experienced combatant and end the fight before it started. This example offers none of that.
There’s something to be said for the take the third option, “do something crazy” mentality for self-defense. However, that involves hopping up and down on one leg while singing a little song until the guy with the knife thinks you’re too much trouble to bother with. This is a real example of how a woman escaped a mugging. People don’t like crazy and the unexpected can throw someone off. However, you’ve got to actually throw them off. This scenario you’ve created for yourself is too much within the range of an actual fight. These are the choices of someone who knows nothing about violence and thinks they’re being out there when the scenario proposed is what I’d expect from someone who doesn’t know what they’re doing. You want someone to go, “what the ever-living fuck was that?” Kill someone with a rubber chicken. Wait, what? how? Who knows, but that’s going to result in some confusion.
So, let’s dig into some advanced concepts that your character wouldn’t begin to understand.
It takes someone a moment to register a threat they’re unaware of. This runs around a quarter of a second for unexpected visual information. That’s basically dead time while their brain is processing what’s happening. (Sound is processed faster, and reflexes from touch stimuli are the fastest at 0.15s.) (All of this is, “average,” so there is some range here.) If you have the capacity to end a fight on the edge of that window, it is impossible for your opponent to respond.
If your character’s cunning plan was to hide behind the door and mace them when their foe entered, that’d work, (with caveats.) If they were behind some sound equipment, they might be able to topple the stack on the other character, though that’d be less effective.
Cymbals? Nope. The sound isn’t going to be debilitating enough, and before you suggest, “but maybe if they’re bigger,” that’s the problem. Small symbols aren’t going to produce enough noise to have any appreciable effect, though you could box someone’s ears with them. If you’re using symbols larger than their head, those will get caught on the target’s shoulders, reducing the impact. At large enough sizes, these will collide with the shoulders, and then each other, meaning there will be little to no force applied to the head. Also, larger symbols are noisier; I don’t mean they make more noise when used, they’ll do that too, but they also produce noise when held, picking up and amplifying small oscillations. Remember the thing a moment ago about reaction times? Actively making noise informs your opponent that you’re there and their brain processes that information faster, telling them where you are, and significantly carving down reaction times.
Giving your position away also significantly reduces your opponent’s reaction delay. Once they know you’re there, they can start preparing to deal with you. Now, in fairness, we’re talking about a difference of less than 100 milliseconds, but in the context of combat, that’s significant. This is also part of why the trained vs untrained thing is such a hard line. If you’ve had sufficient training, you can intelligently react to what you’re seeing, hearing, and feeling. You don’t have to stop and decide what to do next. If you don’t have sufficient training, you need to stop and think between strikes. This means, under most circumstances, an untrained fighter cannot maintain the initiative.
You might also, now, have a better idea of why ambushes work so well. Storming through a door is a good way to take a bullet. Especially if your foe knows you’re coming, they’re listening for you, they’re actively ready, and they only need the visual confirmation to go. This is also introducing us to a lot of problems with your, “expert.”
You didn’t specify how they’re an expert, and that’s kind of an issue, because they’re making a lot of very inexperienced mistakes here.
Your expert has decided to enter a new room. Since you said, “let go,” I’m going to assume they have one of two things, a weapon or a hostage (possibly both.)
Your expert’s first task would be to “sweep” the room. This starts happening as they enter. You divide the room into “pie slices,” from the door, and as you open the door, you verify that there’s no threat, panning from the side opposite the door’s hinges, across until the door is fully open. This means they’re going to see the “musician” before they can act. They’re also actively looking for threats, which means their reaction will be far faster. They’d also use their foot to block the door so that it couldn’t be used against them as a weapon. (I’m working off the assumption that the door opens into the room, because that is how architecture works in most places, the exact process for scanning a room (or corridor) from the other side varies a little, but the basics above hold true.
There is a good element in here; your character has a plan to disorient their foe. This can open up options for finishing the fight. Except, your character doesn’t have a plan to finish the fight. Boxing someone’s ears is disorienting, (though your character would be better off doing that with their bare hands), and it will put an opponent off balance, but it won’t finish a fight. Your character needs a way to incapacitate their foe.
Is it possible to incapacitate a foe through sheer weirdness? Maybe, but probably not. You’d need to come up with an engineer a situation so bizarre your expert decides to throw in the towel and take up a career in making table candles. That’s a kind of strangeness, you’d really need to work up to.
Now, we have other problems with this scenario. Your expert is the driving force behind the pacing for the scene beyond just the fight. If your protagonist is running, then you should assume that they’ve already taken control of the initiative which means the protagonists reactions are a result of the expert’s actions. Outlining those priorities, goals, and skills for yourself will be necessary in working out either a plan of attack or escape. What does the expert want? What is their goal? What are they trained to do? How do they go about achieving that goal?
All these can decide whether or not this expert will even choose to fall into the protagonist’s trap and walk through that door, or simply lock the protagonist in. If the room has multiple exits, they might choose another method of entry. One of the traps you shouldn’t fall into is trying to structure a fight based on what you want the outcome to be. Rather you should create the sequence with a focus on the strengths of these two characters. Grabbing the cymbals is the kind of attack someone without experience thinks is a good idea, so they try it and… it fails. (You’d need a something like a blowhorn, not cymbals to disrupt their concentration.) Now, what?
Depending on your character’s skills, they may have far more effective ways to deal with an expert hunting them, which could be as simple as working to avoid detection and escape. Having a character who isn’t trained to fight doesn’t mean you have an incompetent character, it just means violence isn’t an option they can use effectively. They will need to look for alternative options to achieve their goals.
Cheesing this so that your untrained protagonist can win by brute force weakens every character in your narrative, it diminishes your tension, and if this character is a dragon for another villain then you’ve devalued both of them. You’ve devalued your protagonist too. Focus on what your character is good at, and make their strengths the backbone to their achieving victory. Don’t be afraid to let a scene slip sideways or for a character to lose, if you’ve created a scenario where your character doesn’t have the means to win then let the scene play out. Ask: what happens next?