Yet another form is the portable digital piano which often combines the capabilities of stage pianos, but with additional features similar to a conventional home keyboard. These digital pianos are mostly designed for various purposes such as home, studio, classroom, stage or personal use. It is similar in form to a stage piano, but much lighter in weight, and having a more compact size. Unlike stage pianos, portable digital pianos were commonly equipped with built-in amplification and loudspeakers, usually has lower cost than other types, and its sound quality was often comparable or similar to that of a conventional keyboards due to a simpler sound synthesis system, though some models, often utilize a similar sound generation system as the more advanced model lineups of the same manufacturer. Many of them also contain a wide assortment of sounds, like one would expect from an electronic keyboard, including sound effects and drum kits. Also like conventional keyboards, these digital pianos often feature an automated "rhythm section" function which is controlled by playing chords with the left hand.