The term 'small pianos' can refer to spinets, which are seven-letter instruments that are smaller than traditional upright pianos. Spinets are typically shorter in height and have a shallower depth than regular pianos, making them more compact and easier to move. They also have fewer strings and a shorter soundboard, resulting in a less powerful sound. Despite their smaller size, spinets still produce a full range of tones and are popular among beginner and intermediate players.