There are sounds between almost all basic didgeridoo sounds, since they are not separated by any physical limits. The initial creator of all the sounds is your whole body, and since it is connected inside, these sound creators are often neighbours. Thus, drone and the first toot are also neighbours in a way. It seems they are distinctly separate, but they are not. One thing you can do is gradually change the tension of your lips from the drone to the first toot and you will get notes between them. But that often does not sound most profound, since there is no resonance at these frequencies.

There is another possibility that makes more sense musically. It could be explained as an extension of drone textures to the toots, and it is, naturally, more easily induced on deeper and longer instruments. It is produced by relaxing only a part of lips while playing the first toot. This results in a maintained vibration on the first toot frequency, while simultaneously obtaining new rougher sounds, coming from the ground level of the drone. By different relaxations and tension of lips, you can mix these sounds and get a world of possibilities between your toots. It is to be noted it is specially natural to some didgeridoos, and less natural to others. We don’t know what the cause of this is. Probably something in the black hole.