Vijnana Bhairava Tantra · Dharana 38 · Verse 61
Center between two thoughts
Notice any two things in awareness: two thoughts, two sounds, one thought and the next, two objects in view. Do not choose either one. Set both aside and rest in the interval between them. The center between them is what the text asks you to inhabit.
Older line
When you are aware of any two things, rest in the middle between them. Letting go of both at once, reality shines in the middle.