A sunburst electric guitar's full body and neck, lit against a dark studio background, showing the complete instrument before any signal chain begins.

Week 01 Stage: Input

What Is Guitar Tone?

Photo: Lightburst · CC BY-SA 4.0

What do we actually mean when we say two guitars have different “tone”?

  1. InputA player's touch
  2. ProcessAn eight-stage signal chain
  3. OutputWhat we call tone

No week before this one

Tone as an engineering question

“Tone” gets used loosely — warm, bright, aggressive, muddy. This course treats it as an engineering question instead: two signals can share a pitch and a loudness and still sound completely different, and that difference has a name, a cause, and a measurable signature. This week sets up the vocabulary and the signal chain that the rest of the course keeps returning to. By the end of it you should be able to distinguish pitch, loudness, and timbre as separate properties of a sound; recognise that different waveforms can share a fundamental frequency; read a signal in both the time domain and the frequency domain; identify the stages of the guitar signal chain; and explain why tone is the product of a whole system, not any single component.

  1. Physical mechanism
  2. Signal transformation
  3. Waveform / spectral consequence
  4. Audible consequence

Vocabulary

Pitch, loudness, and timbre

Three separate properties get bundled together in casual listening. Pitch is how high or low a note sounds, and corresponds to the fundamental frequency of the vibration. Loudness is how intense the sound is, corresponding to amplitude. Timbre is everything else — the property that lets you tell a guitar apart from a violin playing the identical pitch at the identical loudness. Timbre itself is shaped by several contributors at once: the balance of harmonics in the spectrum, transient behaviour at the start of a note, how the sound dies away, modulation over time, nonlinear distortion, resonances in the instrument and signal chain, and other temporal effects — no single number captures it; it is the composite of all of these.

Two readings

Time domain and frequency domain

The same sound can be described two ways. A time-domain view — a waveform — plots amplitude against time and shows how a signal literally moves. A frequency-domain view — a spectrum — plots how much energy sits at each frequency, and shows what that motion is built from. Neither view is more “real” than the other; they’re two readings of the same signal, and this course moves between them constantly.

The system

The guitar signal chain

From the string’s first vibration to the sound reaching a listener’s ear, a guitar’s tone passes through every one of these stages — and every stage can change it. That’s why tone is a property of the whole system: the same string and pickup can sound different behind a different set of electronics, pedals, amplifier, speaker, or room, and each week of this course studies one stage of this chain in more depth.

Try it

Same pitch, three timbres

  1. Physical mechanism
  2. Signal transformation
  3. Waveform / spectral consequence
  4. Audible consequence

Sine, square, and sawtooth waves below all play at exactly the same 220 Hz fundamental — the same pitch. Switch between them and look at the waveform and spectrum as you listen: the difference you hear is entirely timbre, built from a different balance of harmonics above that shared fundamental.

Waveform family
Waveform family
One cycle
Harmonic spectrum

Audio never plays automatically — press play to hear it, press again to stop.

All three waveforms play at exactly the same 220 Hz fundamental. Whatever difference you hear is timbre, not pitch — the harmonic content shown above.

Takeaways

What this week establishes

  1. Pitch (frequency), loudness (amplitude), and timbre (everything else) are separate properties of a sound.

  2. Different waveforms can share a fundamental frequency and still sound completely different — that difference is timbre.

  3. The time domain (waveform) and frequency domain (spectrum) are two views of the same signal, not two different signals.

  4. The guitar signal chain runs string → pickup → electronics → pedals → amplifier → speaker → room → listener, and every stage can shape tone.

  5. Tone is a property of the whole system, not any single link in that chain.

The chain

Where this sits, and what comes next

  1. 01INPUT
  2. 02STRING
  3. 03PICKUP
  4. 04CIRCUIT
  5. 05DRIVE
  6. 06DISTORTION
  7. 07FILTER
  8. 08MODULATION
  9. 09SPACE
  10. 10AMP
  11. 11SPEAKER
  12. 12OUTPUT
Week 02 takes it on The Vibrating String

This week has no previous material to connect to — it’s the conceptual starting point for the course. It introduced harmonics and spectra in the abstract, comparing waveforms that already existed. Week 2 asks where those harmonics physically come from in the first place: what happens, mechanically, when a guitar string vibrates.

Teaching date
22 February 2027

Teaching team