A held root or a one-chord bed with nothing pulling anywhere.
ANY parallel mode of the tonic — swap one note, change the whole mood — SCL·05
this is what the next section is for — Ionian, Lydian, Mixolydian… all over the same root MD·01
With no harmony arguing back, the scale you choose IS the tonality. A drone is the one place you can hear Lydian vs Mixolydian side by side over the same note.