2HP Pluck (2013–)

A two-inch-wide module for plucked strings. You may squint a little while you tune it.

Overview

The 2HP Pluck does one thing. It makes plucked-string sounds, using a Karplus-Strong physical modeling algorithm. Settings run from tight, staccato pizzicato to long decays that hang in the air. For such a minimal module, the range is expressive, especially once you start voltage-controlling its parameters. It is a specialist. It won't growl, it won't sweep, and it won't turn into a bass synth. What it does, better than almost anything else in Eurorack, is sound like a string being flicked.

Two horizontal inches holding a four-voice synthesizer was the Pluck's selling point when it launched. That density has a cost. The front panel is spartan: one tiny knob for pitch, another for damping, and a third for decay. No display, no menus, no performance controls beyond what you can route via CV. There's also no distraction, just one algorithm doing one job.

Eurorack already had plenty of physical modeling options when the Pluck arrived. Mutable Instruments' Rings is the obvious comparison. The Pluck didn't compete on features. It doesn't offer modal synthesis or convolution, and it doesn't simulate every resonant body. It just plucks. It became a cult favorite among minimalists, drone artists, and anyone trying to squeeze their rack space to the limit.

Specifications

Manufacturer	2HP
Production Years	2013–
Original Price	$149 USD
Width	2HP
Depth	45mm
Power	+12V: 78mA, -12V: 6mA
Polyphony	4 voices
Synthesis Type	Physical modeling (Karplus-Strong algorithm)
Tracking	Accurate 1V/Oct across five octaves
Inputs	Pitch CV, Gate, Damp CV, Decay CV
Outputs	Audio out
Keyboard Size	N/A (module)
Oscillators	Digital (algorithmic)
Filter Type	Not applicable (damping via algorithm)
Effects	None (pure synthesis engine)
MIDI	No (CV only)
Weight	Approx. 30g (estimated)
Dimensions	4HP height, 2HP width, 45mm depth

Key Features

The Karplus-Strong Engine in a Sliver of Metal

The Pluck relies on the Karplus-Strong algorithm, a digital technique developed in the early 1980s. It simulates a plucked string by feeding a burst of noise through a delay line with a low-pass filter. The method is efficient. It needs minimal processing power and gives organic results. 2HP didn't invent the algorithm, but they got a fully functional polyphonic implementation into 2HP by stripping out everything non-essential - no wavefolding, no resonance shaping, no alternate modes. With a long decay and low damping, the note evolves as it fades. Higher harmonics die away faster than the fundamental, like a nylon or steel string.

Polyphony Without the Bulk

Four-voice polyphony in 2HP was unheard of when the Pluck debuted. Most compact modules at the time were monophonic or faked polyphony with arpeggiation. The Pluck plays four notes at once, chords included. That makes it useful for texture layers, ambient pads, and rhythmic counterpoint. Patch in a sequencer with chord triggers and you get a tiny harp in your mix. The polyphony shapes the sound, too. The voices share the same algorithm and are tightly packed in memory, so they interact in subtle ways - slight detuning, phase nudges - that give chords a natural, slightly imperfect feel. It isn't pristine unison. It's a small ensemble playing in close quarters.

CV Control That Rewards Experimentation

The front panel is sparse, but the Pluck opens up under CV control. The Damp and Decay inputs respond smoothly to modulation. A simple envelope or LFO can take you from a tight, muted jazz bass pluck to a ringing, open-string sustain. Run a slow random voltage into Damp and the string length seems to shift unpredictably, like fingers sliding along a fretless neck. Patch a sample-and-hold to Decay and each note lingers for a different duration, which gives evolving, aleatoric textures. Without modulation, the Pluck can feel static, even sterile. With dynamic control sources, it is far more expressive than its size suggests.

Historical Context

The 2HP Pluck emerged in 2013, as Eurorack was shifting from boutique curiosity to full-blown modular renaissance. Manufacturers were racing to pack more functionality into smaller spaces, and 2HP, founded by engineer and minimalist designer Tony Rolando, was at the front of that movement. The Pluck wasn't the first physical modeling module, nor the most advanced, but it was the first to deliver a convincing, polyphonic string voice in such a small package. Mutable Instruments was gaining acclaim at the same time for powerful, feature-rich modules like Braids and Rings, which offered vast sonic terrain at higher price and space costs. The Pluck didn't try to beat them at their own game. It offered an alternative: do less, and do it in 2HP.

It also reflected a growing appetite for algorithmic synthesis in Eurorack. Analog oscillators and filters still dominated, but digital modules were offering timbres that were difficult or impossible to get from traditional circuitry. The Pluck and the 2HP Bell (its metallic cousin) showed that digital didn't have to mean complex or menu-dense. It could be immediate and focused. The market was getting crowded with "do-anything" modules, and the Pluck went the other way.

Collectibility & Value

The 2HP Pluck has held its value well since its release. Used units regularly sell between $120 and $160 depending on condition, against an original MSRP of $149. It's not a rare module, since production has been steady, but people tend not to flip it. Once you've got a Pluck, you usually keep it, even if you don't use it daily. Its main competition is obsolescence: a Plaits or Shades does this and a dozen other things. Yet the Pluck persists, valued for purity rather than versatility.

It has quirks that affect ownership. The tuning knob is notoriously fiddly - tiny, recessed, and hyper-sensitive. Many users report struggling to dial in precise pitches by hand, especially in low light. Some resort to a toothpick or tweezers. Others patch a quantizer before the pitch CV input and leave the knob at a fixed position. The circuitry isn't at fault, since tracking across five octaves is accurate when properly calibrated. The interface just makes manual tuning a chore. This isn't a module for live tweaking.

The physical construction is minimalist to a fault. The PCB is thin, the jacks are standard-sized but tightly packed, and the module offers no protection against accidental shorts. In a densely packed case, a loose patch cable can bump the knobs or short adjacent pins. Some users put 1HP blank panels on either side to give it breathing room. That eats into the very real estate the module was meant to conserve.

If you're buying used, check for firmware updates. The module has seen no major revisions, but earlier units may benefit from stability patches. Also verify that all four voices trigger consistently. It's rare, but some defective units exhibit voice dropout under certain CV conditions. Power draw is minimal (+12V: 78mA, -12V: 6mA), so it won't tax even the smallest power supplies.