ARP String Ensemble
The ARP String Ensemble, also marketed as the Solina String Ensemble, is a fully polyphonic analog string synthesizer that emulates orchestral string and brass sounds using divide-down oscillator technology, featuring a 49-note keyboard and built-in chorus effects.[1][2][3] Developed by the Dutch company Eminent in 1974 as a derivative of the string section in their 310U organ, the instrument was originally released in Europe under the Solina name before ARP Instruments acquired distribution rights and rebranded it for the U.S. market, with production continuing until 1981.[2][1] It evolved through several versions, including the SE-I (monoaural chorus), SE-II (switchable chorus), SE-III (stereo output), and SE-IV (with LED indicators), all sharing a wooden-paneled design and simple controls for accessibility.[2] Key features include six preset voices—violin, viola, cello, contrabass, trumpet, and horn—that can be activated individually or combined, with the upper voices polyphonic across the full keyboard and the cello and contrabass monophonic in the lower octave for bass emphasis.[1][2] The synthesizer employs a basic envelope generator with adjustable crescendo (attack) and sustain length sliders, alongside global tuning, volume, and a signature analog chorus effect created via three modulated bucket-brigade delay lines, which imparts its lush, shimmering timbre.[1][2] Additional outputs include gate and trigger signals from the keyboard for integration with other gear. Renowned for its warm, ensemble-like string tones, the ARP String Ensemble became a staple in 1970s popular music, appearing on recordings by artists such as Pink Floyd (on tracks like "Welcome to the Machine" from Wish You Were Here), Elton John ("Someone Saved My Life Tonight"), and the Rolling Stones ("Fool to Cry").[2] Its distinctive sound influenced genres from progressive rock to disco, cementing its status as one of the earliest and most iconic "string machines" in synthesizer history.[1][2]History and Development
Origins and Design Process
ARP Instruments, Inc. was founded in 1969 by engineer Alan R. Pearlman in Lexington, Massachusetts, initially under the name Tonus, Inc., with a mission to produce affordable and reliable electronic musical instruments capable of polyphony to compete with established organ manufacturers and monophonic synthesizers like those from Moog.[4] Pearlman, whose childhood nickname inspired the ARP branding, drew from his prior experience at NASA and Worcester Polytechnic Institute to prioritize innovations in modular and polyphonic designs, aiming to bridge the gap between complex studio synthesizers and accessible performance tools.[5] The company's early focus on polyphony reflected the era's demand for instruments that could emulate orchestral ensembles without the limitations of single-voice operation, setting the stage for ARP's expansion into string synthesizers.[6] The ARP String Ensemble originated from a collaboration with the Dutch organ manufacturer Eminent, which developed the core technology as the Solina String Ensemble in 1974, derived directly from the polyphonic string section of Eminent's earlier 310 Unique organ introduced in 1972.[7] Under a distribution agreement, ARP rebranded and marketed the instrument in the United States, adapting it to meet American market needs while retaining Eminent's foundational design for multi-orchestral emulation.[8] This partnership allowed ARP to leverage Eminent's expertise in organ-derived polyphony, transforming a niche organ feature into a standalone synthesizer that captured violin, viola, cello, and other string timbres with ensemble depth. Initial prototypes stemmed from the 310 Unique's testing, where engineers refined the string voices for standalone viability, focusing on lush, layered sounds suitable for rock and orchestral applications.[9] Engineering the ARP String Ensemble presented significant challenges amid the early 1970s transition from monophonic to polyphonic synthesizers, as developers sought to create a compact, cost-effective instrument that delivered true polyphony across 49 keys without relying on shared oscillators or limited voice allocation common in emerging synths.[10] The design incorporated 12 top-octave master oscillators using divide-down technology—adapted from organ circuits—to generate polyphonic voices across the keyboard for authentic string-like timbres, addressing the era's technical hurdles in achieving full polyphony at an accessible price point of around $1,000.[7][11] This approach prioritized orchestral emulation over complex subtractive synthesis, with testing emphasizing stable tuning and ensemble effects to mimic live string sections, though it required overcoming issues like oscillator synchronization in a portable wooden chassis.[12]Release and Production Timeline
The ARP String Ensemble was commercially launched in 1974 by ARP Instruments, Inc. in the United States, coinciding with its release under the Solina String Ensemble name in Europe by the Dutch manufacturer Eminent B.V..[7][1] The instrument, derived from the string section of Eminent's 310U organ, was positioned as an affordable polyphonic option for musicians, with an original MSRP of approximately $1,000 in the US market.[1] Manufacturing took place at Eminent's facility in Bodegraven, Netherlands, where the units were produced through 1981, with estimates suggesting several thousand instruments were built during the run.[7][13] ARP handled distribution and branding for the American market, importing the keyboards from Europe, which introduced some logistical variations compared to the direct European sales under the Solina label.[1] The instrument reached peak popularity between 1975 and 1977, aligning with the height of progressive rock and fusion genres where its lush, ensemble string sounds became a studio staple.[10] Production ceased in 1981 amid ARP Instruments' bankruptcy, marking the end of the original run.[4][6]Technical Design
Sound Generation and Polyphony
The ARP String Ensemble employs top-octave divide-down synthesis, a technique derived from electronic organ technology, to achieve polyphony across its 49-note keyboard spanning four octaves from C2 to C6. This system utilizes 12 discrete oscillators, each dedicated to one note in the top octave (from C6 to B6), with frequency dividers generating the pitches for lower octaves as needed. The violin, viola, trumpet, and horn voices are polyphonic across the full keyboard, while the cello and contrabass voices are monophonic and available only on the lower 20 keys.[7][2][1] The core waveforms are square-based, which are then shaped through fixed low-pass filtering to emulate the timbres of acoustic instruments, producing a warm, ensemble-like character suited for chordal playing. The instrument features dedicated sections for high strings (violin and viola voices), low strings (cello and contrabass voices), and brass emulation (trumpet and horn voices), each with preset tuning and a simple amplitude envelope consisting of a crescendo attack and adjustable sustain length for a natural decay. Unlike voltage-controlled synthesizers, the ARP String Ensemble operates with fixed, non-modifiable tuning and envelopes, prioritizing ease of playability and consistent orchestral simulation over expressive control.[1][14][15] The output is a mono mixdown of the selected sections, with individual volume controls allowing blending before the signal reaches the built-in chorus effect for added depth. This design enables polyphonic performance of complex harmonies with the specified voice limitations, contributing to the instrument's signature lush, layered sound.[1][7]Controls, Effects, and Interface
The ARP String Ensemble features a 49-key velocity-insensitive keyboard, providing a four-octave playing range from C2 to C6 for polyphony without dynamic response to key velocity. The front panel layout centers on six individual on/off switches for the voice sections—violin, viola, trumpet, horn, cello, and contrabass—enabling selective activation and blending of these divide-down-generated timbres to form orchestral ensembles, such as combining violin and viola for a classic string choir effect. The cello and contrabass are monophonic and accessible only on the lower 20 keys.[7][16][17][2] Central to the instrument's iconic sound is the built-in ensemble chorus effect, realized through a multi-stage bucket brigade device (BBD) comprising three parallel analog delay lines, each independently modulated by low-frequency oscillators at slightly varying rates to introduce phasing, detuning, and thickening. This creates the signature "lush" orchestral swell, with three selectable modes (labeled I, II, and III) that engage one, two, or all three BBD stages respectively, allowing users to adjust the effect's depth from subtle widening to full immersive chorus. The voices are mixed post-generation and fed directly into this BBD chorus before the final output, ensuring the modulation applies uniformly to the combined signal for seamless chordal textures.[7][15][18] Additional controls include a master volume knob for overall output level, a crescendo slider that adjusts the attack phase of the envelope (typically ranging from about 50 ms to 400 ms for rapid onset), and a sustain length slider controlling the decay/release duration (adjustable up to 1-2 seconds or more for sustained pads). The panel also provides a 1/4-inch input for an external sustain footswitch to hold notes indefinitely and a dedicated headphone jack for monitoring, though the instrument predates MIDI and includes no CV/Gate inputs, only basic gate and trigger outputs for synchronization.[1][19][16] Operationally, the fixed envelope generator—shared across all voices—employs a simple attack-decay contour optimized for immediate chord response, bypassing complex ADSR programming to prioritize the instrument's role as a performative string pad machine; users simply select voices, set chorus mode, and adjust envelope sliders for on-the-fly tonal shaping, with the polyphonic oscillator foundation ensuring clean, full-range playback without note-stealing for the polyphonic voices.[7][1][19]Models and Variants
Standard Keyboard Model
The standard keyboard model of the ARP String Ensemble, produced from 1974 to 1981, featured a 49-key keyboard spanning approximately four octaves (typically from C2 to C6), providing a compact yet versatile playing range suitable for orchestral string simulations.[13][1] This model was designed as a standalone unit with an integrated keyboard, distinguishing it from any custom or aftermarket variants by incorporating all core components into a single enclosure.[7] The instrument evolved through four main versions, all sharing a wooden-paneled design and simple controls for accessibility:- SE-I: Monoaural output with a permanent chorus effect.
- SE-II: Added a switch for turning the chorus on/off.
- SE-III: Introduced stereo output for enhanced spatial imaging.
- SE-IV: Featured LED indicators on the buttons for improved visibility.[7][20]