What is the Nashville Number System?

What is the Nashville Number System?

The Nashville Number System (NNS) writes chords as scale degrees instead of letter names. The number 1 means the chord built on the key’s 1st note (tonic), 4 is the subdominant, 5 is the dominant, etc. Because numbers are relative, the same chart works in any key—just change the key center and keep the numbers.

How to read NNS

• 1–7: Diatonic scale degrees in the key (major by default for 1, 4, 5; minor for 2, 3, 6; 7 is diminished in major).
• Accidentals: #4 (sharp four), b7 (flat seven) for altered chords or borrowed tones.
• Quality (optional, when clarity is needed): 2m, 5sus, 1maj7, 6m7, 7°.
• Slash bass: 1/3 = tonic chord over the 3rd in the bass.
• Rhythm (often notated with symbols): diamonds (holds), pushes (arrows or carets), bars for measures.

Why NNS in Apostolic Pentecostal music?

• Fast key changes: Worship leaders may jump keys for energy or vocal comfort—numbers make on‑the‑fly modulations easy.
• Vamps and builds: Common I–IV–V vamps, 4→5 lifts, and turnarounds repeat seamlessly with numbers.
• Shouts/Altars: Repetitive progressions (e.g., shout patterns) can loop indefinitely and modulate by whole/half steps.
• Medleys: Chain songs without rewriting chords—keep the same numeric flow in new keys.

Typical progressions you’ll hear

• Modern worship ballad: 1 – 5 – 6m – 4
• Classic chorus: 1 – 4 – 1 – 5
• Turnaround/cadence: 4 – 5 – 1 or 2m – 5 – 1
• Drive/Vamp: 1 – 4 – 5 – 4 (loop) or 4 → 5 build
• Shout pattern (one option): 1 – #1°7 – 2m – 5 (repeat)
• Bass walk (6 to 1): 6m – 5 – 4 – 5 – 1

Examples in keys:

// Key of G:  1–5–6m–4   =>  G - D - Em - C
// Key of Db: 4–5–1      =>  Gb - Ab - Db
// Key of A:  2m–5–1     =>  Bm - E - A
// Key of Bb: 1–#1°7–2m–5 => Bb - B°7 - Cm - F
  

Quick translator (numbers → chords)

Use this small script to turn a number chart into letter chords in any major key.

<script>
// Major scale spelling with diatonic chord qualities
const MAJOR = {
  C:  ["C","D","E","F","G","A","B"],
  G:  ["G","A","B","C","D","E","F#"],
  D:  ["D","E","F#","G","A","B","C#"],
  A:  ["A","B","C#","D","E","F#","G#"],
  E:  ["E","F#","G#","A","B","C#","D#"],
  B:  ["B","C#","D#","E","F#","G#","A#"],
  "F#":["F#","G#","A#","B","C#","D#","E#"],
  "C#":["C#","D#","E#","F#","G#","A#","B#"],
  F:  ["F","G","A","Bb","C","D","E"],
  Bb: ["Bb","C","D","Eb","F","G","A"],
  Eb: ["Eb","F","G","Ab","Bb","C","D"],
  Ab: ["Ab","Bb","C","Db","Eb","F","G"],
  Db: ["Db","Eb","F","Gb","Ab","Bb","C"],
  Gb: ["Gb","Ab","Bb","Cb","Db","Eb","F"]
};
const QUAL = ["maj","min","min","maj","maj","min","dim"]; // I ii iii IV V vi vii°

function nnsToChords(key, numbers) {
  const scale = MAJOR[key];
  if (!scale) throw new Error("Unsupported key: " + key);
  return numbers.map(n => {
    // parse items like "6m7", "#4", "1/3", "5sus4", "7°"
    const m = String(n).trim().match(/^([#b]?)(\d)([^/]*)(?:\/([#b]?\d))?$/);
    if (!m) return n; // return as-is if not matched
    const [, acc, degStr, ext, bassAccDeg] = m;
    let deg = parseInt(degStr, 10);
    // base diatonic note
    let note = scale[(deg - 1) % 7];

    // apply accidental to root if present (# or b on the number)
    const sharp = s => s.replace(/([A-G])b?$/, (m)=> m + "#");
    const flat  = s => s.replace(/([A-G])#?$/, (m)=> m + "b");
    if (acc === "#") note = note.includes("b") ? note.replace("b","") : note + "#";
    if (acc === "b") note = note.includes("#") ? note.replace("#","") : note + "b";

    // default quality if none specified and ext doesn't override:
    let qual = ext || "";
    if (!ext) {
      const q = QUAL[deg - 1];
      qual = q === "maj" ? "" : q === "min" ? "m" : "°";
    }

    // handle slash bass like 1/3
    let bass = "";
    if (bassAccDeg) {
      const acc2 = bassAccDeg[0] === "#" || bassAccDeg[0] === "b" ? bassAccDeg[0] : "";
      const d2 = parseInt(acc2 ? bassAccDeg.slice(1) : bassAccDeg, 10);
      let bassNote = scale[(d2 - 1) % 7];
      if (acc2 === "#") bassNote = bassNote.includes("b") ? bassNote.replace("b","") : bassNote + "#";
      if (acc2 === "b") bassNote = bassNote.includes("#") ? bassNote.replace("#","") : bassNote + "b";
      bass = " / " + bassNote;
    }
    return note + qual + bass;
  });
}

// Demo:
console.log(nnsToChords("Ab", ["1", "5", "6m", "4"]));     // ["Ab","Eb","Fm","Db"]
console.log(nnsToChords("Bb", ["1","#1°7","2m","5"]));     // ["Bb","B°7","Cm","F"]
console.log(nnsToChords("G",  ["1/3","4","5sus","1"]));    // ["G / B","C","Dsus","G"]
</script>
  

Practical tips for your band

• Agree on symbols: Decide as a team how you’ll write minors (m), diminished (°), sus, extensions (7, 9), and pushes.
• Use numbers on the fly: When the leader says “go to 4, build to 5,” everyone moves together regardless of key.
• Guitarists: Capo freely—numbers keep the harmony aligned while voicings stay comfortable.
• Modulations: Step up by a whole/half step—keep the same numeric loop for shouts, vamps, and altar calls.