P33

Objectives

By the end of this chapter you will be able to:

  • Explain what an interval is and name the common intervals.
  • Build a major scale and a minor scale on the PO-33’s chromatic pad.
  • Explain why some notes “go together” and others clash.
  • Recognise major and minor scales by ear.

Musical concept: what is an interval?

An interval is the distance between two pitches. The smallest interval (a single semitone, like C to C#) is called a minor second or semitone. The largest interval in a single octave (twelve semitones, like C to C) is an octave.

The most important intervals are:

  • Minor 2nd (1 semitone): C → C#. Dissonant — sounds tense.
  • Major 2nd (2 semitones): C → D. Consonant — sounds happy.
  • Minor 3rd (3 semitones): C → D#. Consonant — sounds sad.
  • Major 3rd (4 semitones): C → E. Consonant — sounds happy.
  • Perfect 4th (5 semitones): C → F. Consonant — sounds open.
  • Tritone (6 semitones): C → F#. Dissonant — sounds “spooky”.
  • Perfect 5th (7 semitones): C → G. Consonant — sounds stable.
  • Minor 6th (8 semitones): C → G#. Dissonant.
  • Major 6th (9 semitones): C → A. Consonant.
  • Minor 7th (10 semitones): C → A#. Dissonant.
  • Major 7th (11 semitones): C → B. Dissonant.
  • Octave (12 semitones): C → C. Consonant — sounds the same.

Allen (Music Theory for Electronic Music Producers) calls the tritone “the most dissonant interval in Western music”. The tritone appears in jazz (the “Devil’s interval”) and in heavy metal. In pop music, tritones are usually avoided.

Sidebar — consonance and dissonance. These are not absolute categories. They are cultural and historical. Medieval listeners found major thirds dissonant; modern listeners find them consonant. The intervals themselves haven’t changed; our ears have. Listen to a piece of medieval polyphony and notice how the major thirds sound “tense” — that’s because your ear has been trained by modern music to hear them as consonant.

Scales

A scale is a selection of 7 notes (out of the 12 in an octave) that “go together”. The most common scales are:

  • Major scale: a pattern of intervals that sounds “happy”. The C major scale is C, D, E, F, G, A, B, C. Intervals: 2-2-1-2-2-2-1 (semitones from C).
  • Natural minor scale: a pattern of intervals that sounds “sad”. The C minor scale is C, D, D#, F, G, G#, A#, C. Intervals: 2-1-2-2-1-2-2.
  • Pentatonic scale: a 5-note scale that “always sounds good”. The C major pentatonic is C, D, E, G, A. No semitones.
  • Blues scale: a 6-note scale with a “blue” note. C, D, D#, E, G, A.

The major and minor scales are the foundation of Western music. Pentatonic and blues scales are the foundation of popular music (rock, blues, country, folk).

Building a major scale on the PO-33

The C major scale on PO-33 pads:

  • Pad 1: C.
  • Pad 3: D.
  • Pad 5: E.
  • Pad 6: F.
  • Pad 8: G.
  • Pad 10: A.
  • Pad 12: B.
  • Pad 13: C (one octave up).

That’s 8 notes (the 13th is the octave). To play the scale, tap pads in order: 1, 3, 5, 6, 8, 10, 12, 13.

Building a minor scale on the PO-33

The C natural minor scale on PO-33 pads:

  • Pad 1: C.
  • Pad 3: D.
  • Pad 4: D#.
  • Pad 6: F.
  • Pad 8: G.
  • Pad 9: G#.
  • Pad 11: A#.
  • Pad 13: C.

To play the minor scale: 1, 3, 4, 6, 8, 9, 11, 13.

Why some notes “go together”

Notes “go together” because they share overtones (also called harmonics). When you play a single note, you hear not just the fundamental frequency but also its overtones — multiples of the fundamental (2×, 3×, 4×, …). Two notes that share overtones sound consonant. Two notes that don’t, sound dissonant.

For example, C and G share overtones 2×, 3×, 4× — many shared partials. C and C# share only overtone 2× — fewer shared partials, hence more dissonance.

This is why the perfect fifth (C to G) is so consonant: it has the most shared overtones of any interval except the octave.

Sidebar — Hewitt on harmonics. Hewitt (Music Theory for Computer Musicians) has an entire chapter on harmonics. He explains how the overtone series (2×, 3×, 4×, …) gives rise to the intervals of Western music. The fifth (3:2 ratio) and the fourth (4:3 ratio) are the simplest, hence the most consonant. The tritone (45:32 ratio) is the most complex, hence the most dissonant.

PO-33 Playback: writing a melody that stays in key

To write a melody that sounds “right” (i.e., not jarring), restrict yourself to the notes of a single scale. Pick C major: pads 1, 3, 5, 6, 8, 10, 12, 13.

Write a melody using only those pads. Any combination of those pads will sound “in key” — they will not clash.

To write a melody that sounds “wrong”, use the notes outside the scale. For C major, the forbidden pads are 2, 4, 7, 9, 11, 14, 15, 16 (C#, D#, F#, G#, A#, C#5, D5, D#5). A melody that uses those pads will sound dissonant — sometimes intentionally, sometimes not.

Guided exercise: a C major scale melody

Success criteria: a melody that uses only the 7 notes of C major (pads 1, 3, 5, 6, 8, 10, 12) and ends on pad 1 (C, the tonic — the “home” note).

  1. Record a melodic sound into slot 1.
  2. Press WRITE, PLAY.
  3. Tap pads in this sequence, on steps 1, 3, 5, 7, 9, 11, 13, 15: 1, 3, 5, 6, 8, 10, 12, 13.
  4. Press WRITE to exit.

This is a C major scale played as a melody. It should sound “open” and “resolved”. Compare to a minor scale (pads 1, 3, 4, 6, 8, 9, 11, 13) — it should sound “sadder”.

Creative challenge: a melody in C minor

Write the same exercise but in C minor. Use pads 1, 3, 4, 6, 8, 9, 11, 13. Listen to the difference between major and minor. The difference is one note (the third: E in major, D# in minor). One note changes happy to sad. This is the most powerful tool in music.

Listening assignment

Listen to:

  • The Beatles, “Let It Be” (1970). The chord progression is C → G → Am → F (we will get to chords in Chapter 10). The melody is mostly stepwise in C major. The song sounds “hopeful” — major scale, simple chords.
  • Adele, “Someone Like You” (2011). The chord progression is C → G → Am → F → C → G → F → G…wait, same chords as “Let It Be”! But Adele’s version sounds “sad”. Why? The melody uses notes from C minor (not C major). Same chords, different scale — that’s the difference between happy and sad.
  • Led Zeppelin, “Stairway to Heaven” (1971). The intro is in A minor. The famous chord progression descends: Am → G → F → E → D → C → D → Am. Each chord is a step lower. The song moves from minor (sad) to major (resolved) over 8 minutes.

Summary and checkpoint

Key takeaways:

  • An interval is the distance between two pitches. Common intervals are named (minor 2nd, major 3rd, etc.).
  • A scale is a selection of 7 notes. Major scales sound happy; minor scales sound sad.
  • Pentatonic scales (5 notes) “always sound good”. The C major pentatonic is pads 1, 3, 5, 8, 10.
  • Notes “go together” because they share overtones.

Self-check:

  • [ ] Can you build a C major scale on the PO-33 pads?
  • [ ] Can you build a C minor scale on the PO-33 pads?
  • [ ] Can you write a melody using only the notes of C major?
  • [ ] Do you understand why the perfect fifth is so consonant?

If you answered “yes” to all four, move on to Chapter 9.