The article linked to above does show how to adjust equalization - I have just tried experimenting with it, while playing music from my iTunes library (not Apple Music), and trying various manual adjustments that were deliberately large enough so that I could easily tell if it made a difference, repeating portions of a particular track after making changes. It
does work with the HomePod.
From the article:
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First, open
iTunes and connect to HomePod by clicking on the
AirPlay icon located to the right of the volume slider. Select
HomePod and begin music playback.
Next, navigate to
Window > Equalizer in the menu bar and either select a
preset or
drag the frequency sliders to increase or decrease volumes of individual frequencies. The
Preamp slider controls adjustments to overall volume of all frequencies, but these modifications can come at a cost to fidelity.
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I then went to my iPhone and made changes there, using the 'Music' settings. This
did not affect the setting for EQ in iTunes.
By the way, it takes a short period of time for settings made using iTunes on the computer to get to the HomePod, maybe just a second or two but there is a lag. I suspect that there is some buffering going on, and so the HomePod takes a short amount of time to adjust to anything changed from the computer. This is also what I've observed when changing volume levels or song selections, anything that affects what the speaker is being told to do.