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Why synth guitars sound fake

Written 2026-10-27. Based on established acoustics and audio DSP knowledge.

A real plucked string is never static and never repeats itself. Simple synth guitars use models far too simple to capture that, and everyone has heard thousands of real guitars, so small departures register as "wrong" without any training.

What a real string does

The string itself

  • Each harmonic decays at its own rate. Highs die fast and lows ring on, so the tone darkens every millisecond.
  • Inharmonicity. String stiffness pushes upper overtones slightly sharp of perfect multiples. Without it, a tone sounds electronic.
  • Pluck position. Plucking near the bridge is bright, and near the neck is round. The pluck point cancels specific harmonics, acting like a comb filter.
  • Two planes of vibration. Vertical and horizontal motion decay at different rates and exchange energy, which gives a two-stage decay and gentle beating.
  • Pitch glide. A hard pluck stretches the string, so the note starts slightly sharp and settles.

Around the string

  • Body resonance. An acoustic guitar body has dozens of resonant modes that color each note differently.
  • Sympathetic strings. Unplucked strings ring along faintly.
  • Non-note noise. Pick attack, finger squeak on wound strings, fret buzz, release clicks.

The player

  • No two notes are identical. Exact repetition causes the "machine-gun" effect.
  • Transitions carry realism. Slides, bends, hammer-ons, vibrato, and how notes overlap. Sample libraries often fall apart in phrases even when single notes sound great.

Electric guitars

The amp and cabinet distort and filter nonlinearly, and the guitar can feed back. A raw synth tone without that chain sounds nothing like an electric guitar.

Physical modeling

The from-scratch approach (compute every sample from a model of the physics) has a name: physical modeling.

  • Karplus-Strong (1983): a burst of noise looping through a short delay line with a gentle low-pass filter. It's about a dozen lines of code and is surprisingly string-like, because the loop naturally makes high harmonics die faster.
  • Digital waveguide models (Julius O. Smith, Stanford CCRMA) extend this. Each behavior above becomes its own component: stiffness, pluck position, two polarizations, a body filter, per-note variation.

Strings are a good first target. The physics is well understood, and each improvement is a separate thing you can hear and judge.