I actually learned something new from the weekly Alexa email. I knew that the echos had bass and treble (through voice control), but there is also an "equalizer" (there is bass, treble, and midrange).
And it is always something with Alexa/Echo. It used to say "OK" when setting these, but now there is no response other than the ring light (which made me think the voice commands weren't working). I have brief mode disabled (I tried both enabled and disabled).