Soundwave's creations in tape mode fit perfectly into the cassette hatch in his chest that's designed to carry them. Theoretically, all 12 of them (Selenia does not have a tape mode) can fit inside at once, though the precise physics of this are not well-understood outside of a small, specialized group of scientists. In actual fact, half or more of the cassettes are usually out in the world, moving around in their robot or animal modes. When they do return, they find "Soundwavespace" to be a very safe and comfortable place; there is a sense that the outside world is a million lightyears away and that they are absolutely secure and protected. In this mode they can shut down and go dormant, shielded from whatever outside disturbances may be going on - or, they can choose to link their minds to a sub-portion of Soundwave's, and experience a virtual reality simulator of sorts. In its most basic form, it lets them look out at the world through Soundwave's senses and see what he sees, hear what he hears - provided that he allows it. Or, they can turn their attention inward and partake of Soundwave's knowledge on a wide variety of subjects. Those who are less interested in furthering their mental education can engage a simulator that allows them to experience any scenario they choose - games, combat training, adventure stories - limited only by their imagination. It's a bit like setting the parameters for a waking dream and then letting it play out - all while remaining physically motionless, silent, and enclosed in a fairly small area.