Metal: Hellsinger wants you to fire your guns (or swing your sword) to the beat.
This feels great, obviously.
In this moment, Metal: Hellsinger makes perfect sense.

There are also satisfactions to be had other than remaining on beat or maintaining that multiplier.
This is where the Doom (2016) comparisons come in.
So you’ll change.

Metal: Hellsinger had effectively taught me to hit the cymbal on every third beat.
Once I’d gotten the hang of this, the combo multiplier came into play again.
This left no opportunity for collecting health at all.

There are two solutions.
Each level then ends with the same boss, with new attacks and twists added to elevate the challenge.
I suspect a certain kind of player will surrender to the repetition by choice.

You score points during play, after all, and there are global leaderboards to climb.
I won’t go to those lengths myself.
I’m content with this decision.