I don't think any of these are very useful descriptions. Having studied this some, and discussed it with some people who were saturated in the culture, here are some possible thoughts:

Dreamtime is to this world as dreaming is to our waking: but suppose that instead of our waking time creating the material for dreams, it was the other way around. Then the world we see during daylight would be a crystalized or realized part of the dream. If the dreamtime is the real time, then our waking time is its creature: dreamtime is always there, our waking time passes, and seems to pass forward. The images, animals, spirits, mixed figures that appear in dreams would be the inchoate pre-crystallised matrix of creatures -- so, for example, suppose in a dream you saw a mermaid, then when the dream "woke" into everyday, the fish part would have made fish, and the maid part made woman. The dream holds reality in suspension, awaiting daybreak (making daybreak in fact, out of the earlier daynight). In dreams, rituals, visions, we can go back (not back, but into) dreamtime, to the origin of things to refresh our sense of the infinite nature of being, the temporariness of our categories, etc.
There is more to be said about the singing -- singing looks as if it moves forward, but it too comes out of a pre-singing origin, music (whatever music is). When we sing, we sing something into existence, we choose a key or a tune. This is a metaphor for what happens when the dreamtime sings landscapes or beings into existence: song is being(s).

Hope this helps.

yours,

Peter T.