The Roland D-50 is a linear/polyphonic 61-key synthesizer made by Roland. It was released in 1987. Its features include Linear Arithmetic synthesis, on-board effects, a joystick for data manipulation, and an analog synthesis-styled keyboard layout. The external Roland PG-1000 programmer could also be attached to the D-50 for more complex manipulation of sounds. It was also produced in a rack-mount version. This was called the D-550 and had almost 450 user-adjustable parameters.