Interesting, I experimented a bit with this when my daughter was younger. I used to walk around the room with her in my arms singing to get her to sleep. To ensure she would be settled I would then count 300 steps before putting her in the cot. I discovered I could count and sing at the same time by visualising the number in my head, instead of using my inner monologue. But it requires more focus to maintain.

Thankfully these days she can get herself to sleep. But I miss it sometimes