KiMiASound Design
Level 1 · Foundations›Module 1 · Sound for keyboard players
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Module 1 · Lesson 5 of 5

Seeing sound: waveform, spectrum and spectrogram

Throughout this course you will see sound as well as hear it. Three pictures do almost all the work: the waveform, the spectrum and the spectrogram. Learn to read them here, and every figure in the course will speak to you.

14 minHeadphones or studio monitorsKiMiA and your keyboard
In this lesson you will
  • Read the three pictures this course uses
  • Find pitch, harmonics and time in a spectrogram
  • See how a note lives: strike, bow, breath and organ

01One note, four pictures

A sound changes in two directions at once: from moment to moment, and from low frequencies to high ones. Each picture in this course shows one slice of that.

Figure 1.5.1

One plucked note, four pictures

A KiMiA plucked string (the Comb filter) · C3
1 · Waveform: a few cycles, the shape of the vibration
cycle 1cycle 2
2 · The whole note: how its level changes over time
0 s0.5 s1 s1.5 s2 s2.5 sKey up
3 · Spectrum: which harmonics, how strong (at 0.15 s)
1002005001k2k5k10k0-20-40-60dBHz
4 · Spectrogram: harmonics over time
1002005001k2k5k10kHz0 s0.5 s1 s1.5 s2 s2.5 s
Audio example — listen in the online course
The same sound, four ways. The waveform shows the shape of the vibration; the whole-note view shows its level from strike to silence; the spectrum shows the harmonics at one moment; the spectrogram shows every harmonic over the whole note, and here it shows something the others can’t: the high harmonics die away long before the low ones.
  • The waveform shows the air pressure over a few thousandths of a second: the shape of the vibration. It tells you about the recipe in a rough way (sharp corners mean bright), but two sounds with the same harmonics can look quite different here.
  • The whole-note view zooms out to seconds: how loud the note is from the moment you press the key until it is silent. This is its life in time, its envelope.
  • The spectrum shows the harmonics at one moment: one line for each, its height the level in decibels. It is the clearest picture of a sound’s recipe.
  • The spectrogram puts the spectrum on a timeline: time runs to the right, frequency upward, and brightness is loudness. It is the most complete of the four, and the one you will see most in this course.
Pro tip

Notice that the frequency axes are not even: the distance from 100 Hz to 200 Hz is the same as from 1 kHz to 2 kHz. Each of those steps is an octave, and spacing frequencies by ratio matches how the ear hears pitch. The level axes are in decibels for the same reason.

02Reading spectrograms

Four kinds of sound, four very different pictures:

With a little practice you can read music from a spectrogram: the fundamental is the lowest line of each stack, its height is the pitch, and the stack’s brightness tells you how rich the sound is. Watch for three things in every spectrogram in this course: which lines are there (the recipe), how bright they are (the balance), and how they change (the life of the note).

03How a note lives

The harmonics are only half of a sound’s identity. The other half is time. Hold a key for the same length on four instruments and the notes behave in four different ways:

Figure 1.5.3

How a note lives: four families

Key held for 1.8 s · C4
Struck or plucked: a sudden start, then it can only fade
0 s0.5 s1 s1.5 s2 s2.5 sKey up
Bowed: swells in, holds while the bow moves
0 s0.5 s1 s1.5 s2 s2.5 sKey up
Blown: a breathy start, steady while the breath lasts
0 s0.5 s1 s1.5 s2 s2.5 sKey up
Organ: on, steady, off: no life of its own
0 s0.5 s1 s1.5 s2 s2.5 sKey up
Switch while it plays: same moment, different sound Audio example — listen in the online course
Every instrument has a typical life for each note: how it starts, whether it holds, how it ends. These four KiMiA sounds copy the four families. Module 7 shows you how to shape this life with envelopes, and why it matters as much as the harmonics.
  • Struck and plucked (piano, guitar, harp, mallets): all the energy arrives at once, then the note can only fade, its high harmonics first.
  • Bowed (violin, cello): the note swells in as the bow grips, and holds for as long as the bow moves.
  • Blown (flute, brass, voice): a breathy, sometimes noisy start, then a steady tone while the breath lasts, often with vibrato.
  • Organ: on, steady, off. The note has no life of its own; the player does all the shaping.
At the keyboard

The first few hundredths of a second, the attack, carry much of an instrument’s identity. Cut the attack off a piano recording and it can sound like an organ or a bell. When you design sounds, the start of the note deserves as much care as its color. You will learn to shape it with envelopes in Module 7.

04Seeing sound in KiMiA

Everything in this lesson, KiMiA shows live while you play. At the top of Edit, the Live output strip has four displays side by side. Here they are with 01 · Bowed Saw playing A4:

Figure 1.5.4

KiMiA’s live displays: 01 · Bowed Saw on A4

KiMiA’s Live output strip: the steady saw-like wave, the spectrum, the harmonics of A4 as bars, and the meters
  1. The wave steady, at the newest note’s pitch
  2. The spectrum every frequency, low to high
  3. Harmonics each harmonic of the note as a bar
  4. The meters left and right peaks, loudness in LUFS
The same four pictures as this lesson, live: the waveform, the spectrum, the harmonic series of the note, and the level. The bars fall away from the first harmonic, the saw’s recipe, and thin out above the low-pass at 2.8 kHz; a few dip and come back as the two slightly detuned saws drift against each other.

Click Waterfall above the third display and it becomes a small spectrogram: the spectrum over time, the newest at the top. Here is 01 · Breath Flute playing a melody; each note is a new set of bright lines.

Figure 1.5.5

The Waterfall: 01 · Breath Flute playing a melody

KiMiA’s Live output strip with the Waterfall display: the spectrum over time
With Waterfall chosen, the third display is a spectrogram of the last three seconds, the newest at the top: each note of the flute is a new step of bright lines as the melody climbs and falls. Its breath shows in the spectrum beside it, as the low haze from 1 to 10 kHz.

Further down the page, the Live waveform panel draws the sound over the last few seconds, the way the waveforms in this lesson do: each note’s attack and release, and how loud it is. Its readings give the peak in dBFS and the loudness in LUFS (Lesson 1.4).

Figure 1.5.6

Live waveform: the last seconds

KiMiA’s Live waveform panel: the melody over the last five seconds, left channel above the line and right below
Left above the line, right below, the newest at the right. The outer shape is the peak, the bright core the RMS: the body you hear.

Keep an eye on these displays while you work through the next modules. Connecting what you see to what you hear is how you develop a sound designer’s ear, and after a few weeks you will read a sound’s harmonics off the screen as easily as a chord chart.

At the keyboard

Above the displays, choose what they show: the layer you are editing (Layer A), the whole patch, or the whole Output. Lock at top keeps them in view while you scroll down to any control.

05Try it

  1. Watch the waves. Load 01 · Pure Sine and open Edit. Find the Live waveform · output panel and switch Osc 1 between Sine, Tri, Saw and Pulse while you hold a note. Match each shape to the figures in Lesson 1.3.
  2. Read a spectrogram. Look back at the four spectrograms above. Without listening, say which one is the chord, which is the melody and which is the noise. Then check by playing them.
  3. Four lives. Play the same short melody on 01 · Bell Bar, 01 · Bowed Saw, 01 · Breath Flute and 01 · Harmonic Organ. Which family is each one closest to?
  4. Your instrument. Think of the acoustic instrument you know best. Write down how a note starts, holds and ends on it.
Your notes · the life of a note on your instrument

06Check yourself

Q1Which picture shows how a sound’s harmonics change over time?
The spectrogram plots frequency against time, with brightness as loudness, so every harmonic’s rise and fall is visible.
Q2In a spectrogram, what does a cloud spread across every frequency, with no lines in it, usually mean?
Pitched sounds make lines (their harmonics); noise has no harmonics and spreads its energy across every frequency.
Q3Why are this course’s frequency axes spaced by ratio, not evenly?
An octave is a doubling wherever it falls, and the ear hears every octave as the same step, so the axis gives each octave the same space.
Q4Which family has a note that can only fade after it starts?
A hammer or a pluck delivers all the energy at once; after that the string can only lose it. Bows and breath keep feeding energy in.