The Roland D-50 is a polyphonic 61-key synthesizer

Synthesizer

A synthesizer is an electronic instrument capable of producing sounds by generating electrical signals of different frequencies. These electrical signals are played through a loudspeaker or set of headphones...

 produced by Roland

Roland Corporation

is a Japanese manufacturer of electronic musical instruments, electronic equipment and software. It was founded by Ikutaro Kakehashi in Osaka on April 18, 1972, with ¥33 million in capital. In 2005 Roland's headquarters relocated to Hamamatsu in Shizuoka Prefecture. Today it has factories in Japan,...

. It was released in 1987. Its features include Linear Arithmetic synthesis

Linear Arithmetic synthesis

Linear Arithmetic synthesis, or LA synthesis, is a term that was invented by the Roland Corporation when they released their ground-breaking D-50 synthesizer in 1987.- Overview :...

, on-board effects, a joystick for data manipulation, and an analog synthesis-styled layout design. 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 variant design, the D-550, with almost 450 user-adjustable parameters.

The D-50's capabilities could be modified through the addition 3rd-party products by Musitronics, most notably the M-EX which made the D-50 multitimbral (the D-50 was bi-timbral), as well as a chip that improved the D-50's response to incoming MIDI commands and a system for burning custom PCM cards with user samples for playback in the D-50.
The D-50 was the first affordable synthesizer to combine sample playback

Sample-based synthesis

Sample-based synthesis is a form of audio synthesis that can be contrasted to either subtractive synthesis or additive synthesis. The principal difference with sample-based synthesis is that the seed waveforms are sampled sounds or instruments instead of fundamental waveforms such as the saw waves...

 with digital synthesis

Digital synthesizer

A digital synthesizer is a synthesizer that uses digital signal processing techniques to make musical sounds.Electronic keyboards make music through sound waves.-History:...

, a process that Roland called Linear Arithmetic synthesis

Linear Arithmetic synthesis

Linear Arithmetic synthesis, or LA synthesis, is a term that was invented by the Roland Corporation when they released their ground-breaking D-50 synthesizer in 1987.- Overview :...

.