Between "doing" there is "thinking".
Between "achieving" time there is "planning" time.
We can reduce the time to do something by being familiar with the process that achieves the actual work done. We repeatedly practice the process until we can do it in our sleep. Then we have removed the thinking time and only use time doing.
Between time can also be thought of as the links between each moment.
We are moving through time at 1 second pre second like it or not. We don't always perceive time as a smooth unbroken thread, we break it up into bits.
The links between the bits are the between time. The time when we can be distracted or lead in another direction.
If we use rhythm to synchronise our bits, then the between time has a direction toward the next bit in the cycle, we are less likely to wonder off track.