Sometimes just called a positive, it is a small, usually one-manual, pipe organ that is built to be more or less mobile. It was common in sacred and secular music between the 10th and the 18th centuries, in chapels and small churches, as a chamber organ and for the basso continuo in ensemble works. The smallest common kind of positive, hardly higher than the keyboard, is called chest or box organ and is especially popular nowadays for basso continuo work; positives for more independent use tend to be higher.