The Siel Orchestra is an analogue subtractive 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...

, which was produced by Italian manufacturer Siel

Siel

Societa Industrie Elettroniche was an Italian company that made electronic organs and synthesizers in the 1980s.- Timeline of major products :* 1979 - Orchestra Societa Industrie Elettroniche (SIEL) was an Italian company that made electronic organs and synthesizers in the 1980s.- Timeline of...

 from 1979 to 1982. The original Orchestra was very limited but still a very characteristic instrument for its time. It produces its sounds from a divide-down oscillator network and therefore has 49 note (unlimited) polyphony. Although it contains 4 sections of presets (Brass, Strings, Reed and Piano), each which contain two sounds, the only parameters that can be edited are Vibrato (LFO), Brilliance (for the Brass, which also has a separate 'Brass Attack'), Attack and Decay. This ultimately means that the Orchestra cannot produce many different sounds; however because of its Italian origin and its distinctive routing, the Orchestra sound is not matched by any other similar synthesizers.

The Orchestra was later bought by ARP Instruments

ARP Instruments, Inc.

ARP Instruments, Inc. was an American manufacturer of electronic musical instruments, founded by Alan Robert Pearlman in 1969. Best known for its line of synthesizers that emerged in the early 1970s, ARP closed its doors in 1981 due to financial difficulties...

 to be slightly modified, relabeled and then sold as the ARP Quartet. This version replaced the Reed section with an Organ one, however aside from that the synthesizer was almost identical.

The Orchestra does not support MIDI or any other means of communicating with other electronic instruments, however it does include a volume pedal socket which could be mistaken for a MIDI port.

Orchestra 2

Later, a more programmable version of the Orchestra was released. It still used 4 preset sections, however it offered many improvements over the original version. A better filter for the brass section was included and more sounds were added to other sections. It also introduced a very simple LFO, a graphic equalizer, octave transpotion and an 'animator section' which was effectively a flange effect. It also had a pitch bend function which was surprisingly never included with the first version Orchestra.