P33

Objectives

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

  • Explain what pitch is and how it relates to frequency.
  • Identify the 16 notes of the chromatic scale (C, C#, D, D#, E, F, F#, G, G#, A, A#, B, C, C#, D, D#).
  • Play a melody on the PO-33 by tapping different pads in sequence.
  • Recognise the difference between a stepwise melody and a leaping melody.

Musical concept: what is pitch?

Pitch is how high or low a note sounds. A bass guitar is low-pitched. A piccolo is high-pitched. Pitch is measured in Hertz (Hz), which is cycles per second. Middle C (C4) is 261.63 Hz. The A above middle C (A4) is 440 Hz. The C below middle C (C3) is 130.81 Hz — half the frequency of C4.

Hewitt (Music Theory for Computer Musicians) introduces pitch as “the perceived frequency of a sound”. Lower frequencies sound lower; higher frequencies sound higher. The relationship between pitches is what we call music.

Two pitches that are twice the frequency of each other sound the same — they are an octave apart. C3 (130.81 Hz) and C4 (261.63 Hz) are an octave apart. C4 and C5 (523.25 Hz) are an octave apart. The octave is the most fundamental interval in music.

Sidebar — the chromatic scale. Between C and the next C there are 12 equal steps on the modern Western scale. These 12 steps are called semitones. C → C# is one semitone, C# → D is one semitone, …, B → C is one semitone. The 12 semitones of one octave are: C, C#, D, D#, E, F, F#, G, G#, A, A#, B. The 13th note (the next C) is the start of the next octave.

The PO-33’s chromatic pad layout

The PO-33’s melodic slots (1–8) play a chromatic scale one octave wide. Specifically, the firmware’s auto-mapping helper (F-005) assigns:

  • Pad 1: C4 (middle C).
  • Pad 2: C#4.
  • Pad 3: D4.
  • Pad 4: D#4.
  • Pad 5: E4.
  • Pad 6: F4.
  • Pad 7: F#4.
  • Pad 8: G4.
  • Pad 9: G#4.
  • Pad 10: A4.
  • Pad 11: A#4.
  • Pad 12: B4.
  • Pad 13: C5 (one octave above middle C).
  • Pad 14: C#5.
  • Pad 15: D5.
  • Pad 16: D#5.

So pressing pads in sequence 1, 3, 5, 6, 8, 10, 13 plays the notes C, D, E, F, G, A, C — the C major scale in root position.

Sidebar — the original PO-33 vs. Ravine: Phoenix. The original PO-33 has the same mapping: pad 1 = C4, pad 16 = D#5. The Ravine: Phoenix firmware’s amy_bridge_auto_note_for_step() helper implements this. We use MIDI note numbers 60 (C4) to 75 (D#5).

Stepwise motion vs. leaps

A stepwise melody moves by one or two semitones at a time. Pad 1 → pad 2 → pad 3 is stepwise (C → C# → D). A leaping melody jumps by 5+ semitones. Pad 1 → pad 8 is a leap (C to G, a perfect fifth).

Stepwise motion is calm and singable. Leaping motion is dramatic. Most melodies use a mix of steps and leaps. A melody that only steps is boring. A melody that only leaps is exhausting.

PO-33 Playback: playing a melody

To play a melody on the PO-33, you simply press pads in sequence. Each pad is a different note.

To write a melody into the sequencer:

  1. Record a melodic sound into slot 1 (hold REC + pad 1, sing a single note, release REC).
  2. Press WRITE. Press PLAY.
  3. On step 1, press pad 1 (C4).
  4. On step 3, press pad 3 (D4).
  5. On step 5, press pad 5 (E4).
  6. On step 7, press pad 8 (G4).
  7. On step 9, press pad 6 (F4).
  8. On step 11, press pad 5 (E4).
  9. On step 13, press pad 3 (D4).
  10. On step 15, press pad 1 (C4).
  11. Press WRITE to exit.

You have just written “Twinkle Twinkle Little Star” into the PO-33. The pattern is: C, D, E, F, G, F, E, D, C. This is the simplest melody in Western music — and now it lives on your PO-33.

Trim and tuning

The PO-33’s Tweak Tone mode lets you adjust the pitch and volume of a melodic slot. By default, the slot plays at its recorded pitch (C4 if you sang a C, A4 if you sang an A). You can shift the pitch up or down by an octave with Knob A or B.

To enter Tweak Tone mode: tap the FX button until the mode reads TONE (TONE is the default after power-up). Knob A adjusts pitch (up/down by semitone). Knob B adjusts volume. The screen shows the current pitch in semitones.

Sidebar — pitch shifting. If you recorded a vocal at A3 (220 Hz) but you want it to play at A4 (440 Hz), shift the pitch up by 12 semitones (one octave). The PO-33 does pitch shifting via AMY’s resampler. Quality degrades at extreme shifts (more than one octave), so keep shifts small.

Guided exercise: write “Mary Had a Little Lamb”

Success criteria: you have a melody that plays the notes E, D, C, D, E, E, E, D, D, D, E, G, G (the “Mary Had a Little Lamb” melody in C major).

  1. Record a melodic sound into slot 1 (sing a single note — any pitch is fine; the PO-33 will remap it to C4).
  2. Press WRITE, PLAY.
  3. Step 1: pad 5 (E).
  4. Step 3: pad 3 (D).
  5. Step 5: pad 1 ©.
  6. Step 7: pad 3 (D).
  7. Step 9: pad 5 (E).
  8. Step 11: pad 5 (E).
  9. Step 13: pad 5 (E).
  10. Step 15 (wait — there are 8 notes left; pad 3 (D) twice, pad 3 (D) twice, pad 5 (E) once, pad 7 (G) once, pad 7 (G) once).

Actually, “Mary Had a Little Lamb” has 13 notes. The PO-33 has 16 steps. Use steps 1–13. The last three steps (14, 15, 16) are empty. The pattern will loop every 16 steps, but only 13 of those steps have notes.

  1. Press WRITE to exit.

You have written “Mary Had a Little Lamb”. Listen to it at 80 BPM (Hip Hop). It sounds…wrong. Why? Because the melody is meant to be played at 100–120 BPM, and at 80 BPM each note is held too long.

  1. Tap BPM to cycle to Disco (120). Now it sounds more like a song.

Creative challenge: write your own melody

Pick a melody you know by heart (a nursery rhyme, a TV theme, a pop song hook). Write it into the PO-33 by tapping the pads in sequence.

If you don’t know any melodies, sing “do re mi fa sol la ti do” (the solfège scale) and write that. It’s eight notes, one per odd step.

Listening assignment

Listen to:

  • The Beatles, “Yesterday” (1965). The melody is stepwise: F → E → F → E → F → E → D → C → B → A → G → F. Almost every interval is a step. The song is famous because the melody is so singable.
  • The Beatles, “A Hard Day’s Night” (1964). The famous opening chord is a chord, not a single note — we’ll get to chords in Chapter 10. But the melody that follows is leaping: G → F# → G → A → G → F# → G → A. Big leaps.
  • Beethovern, “Für Elise” (1810). The melody is mostly stepwise, but it includes one big leap (the “E-D#-E” motif). Most classical melodies mix steps and leaps.

Summary and checkpoint

Key takeaways:

  • Pitch is frequency. Middle C is 261.63 Hz. Octaves double the frequency.
  • The chromatic scale has 12 semitones per octave. PO-33 pads 1–16 play C4 through D#5.
  • Stepwise melodies are singable. Leaping melodies are dramatic. Mix them.
  • Tweak Tone mode shifts pitch (Knob A) and volume (Knob B).

Self-check:

  • [ ] Can you name the 12 notes of the chromatic scale?
  • [ ] Can you play “Mary Had a Little Lamb” on the PO-33 pads?
  • [ ] Can you explain why stepwise melodies are singable?
  • [ ] Can you use Tweak Tone to shift the pitch of a recorded sample?

If you answered “yes” to all four, move on to Chapter 8.