Originally Posted by Mike HP.
I've since learned that the thing about reducing the volume only applies to MIDI-Drums, not to Realdrums.
Yup, that's correct. Most Realdrums are mixed down to a stereo mix, meaning that individual drum volumes cannot be changed.

Originally Posted by Mike HP.
Correct, ultimately I will probably have to regulate this with a dynamic equalizer (e.g. Sonible "Smart EQ 4" or "Frequency" from Cubase Pro) that influences the corresponding frequencies.
Check out TDR Nova, it's a fantastic free dynamic EQ and I find it often works great for these kinds of changes. The upgraded paid version is inexpensive and adds expansion instead of just compression, well worth it imho.

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