Klack is a native app written fully in Swift that focuses on speed, hence there is no lag in the audio feedback from pressing keys like some other apps.
Focuses on modern popular keyboard switches rather than for example typewriter sounds. Randomized pitching makes sound way more unique every key press.
Supports up/down keys separately, the result is way more realistic compared to playing both the sounds simultaneously.
Has a negligible RAM footprint and is worth running all the time.
This is one of those apps that you don't think you need or might need, until you use them.
It was a delight for me to immediately find out that the money on the app was really well spent!