u/ExasperatedRabbitor

I’ve been working on voicings that combine a minor triad with an octave doubling on the root—for example, Fm (F-Ab-C) plus F an octave higher, or the same with Cm.
The chord itself isn’t difficult to grip, and my hands are large enough that spanning a ninth is no problem. But adding that octave doubling while keeping everything relaxed and tension-free? I struggle with it, especially when switching between positions quickly.
What’s interesting is that the major versions of these chords (F major + F octave, for instance) feel completely natural—no tension at all. So I suspect the issue is specifically the black key involved as the third note in the minor triad.
I’ve noticed in several YouTube videos that pianists execute these voicings effortlessly, sliding between them without any apparent difficulty. I’m wondering if there’s a specific technique or fingering approach I’m missing.
Any suggestions on how to approach this more efficiently?

I'm now into the piano game for roundabout 1.5 years, never had any other music theory lessons before, and I learned quite a lot of music theory while learning the famous 1st movement of Beethovens moonlight sonata (Neapolitan 6th chord, I love you :) )

Anyway, as many beginners I struggled for a long time with the flat side of the circle of fifths. Now I started learning interpretations of some famous Pop Songs, namely by Phil Collins and Elton John. Many of them are in the key of of F minor, Db major or Eb major. So I got quite used to Bb , Eb, Ab and Db chords in all kind of variations and inversions.

The song that brought my attention to the question I'm going to ask is the famous pop ballade "against all odds" by Phil Collins. It starts off with a Db + Eb in the right hand over a Eb in the flat, followed by the melody going Ab, Bb, Gb and F. So technically this an Eb7sus4 chord (Eb in the bass, right hand Eb Gb Ab Bb Db).

But when transposing this intro just a half step up, so playing D+E in the right hand over E in the bass, followed by the melody going A, B, G and F# it sounds... just awful.

Why is that? Shouldn't it theoretically make no difference at all? Does it have to do with our TET piano tuning and some notes being a few cents off?

And how the heck did Phil and Elton when starting to compose famous pop songs come up that in those keys of Db, Ab, Eb (and their relative minors) and so on some gorgeous sounding chord progressions can be made?