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Section 7.1 Roman Numeral Chord Symbols

Music is full of patterns that are similar from one piece to the next. As we saw with minor scales, we were able to use scale degree numbers to show the different patterns for harmonic, melodic, and natural minor, despite the fact that there are 15 minor key signatures. Using numbers instead of note names helps us see these patterns. Thinking of music in terms of numbers is also helpful with transposition, which means moving melodies and/or chord progressions from one key to another. Thinking of music in terms of numbers also helps us to analyze it and to spot similar patterns between many different pieces in different keys.

We will use Roman numerals to represent chords within a specified key. The Roman numeral “\(\left.\text{I}\right.\)” represents a triad built on \(\hat{1}\) , or the 1st note of the scale. Uppercase Roman numerals represent major triads and lowercase Roman numerals (e.g., “\(\left.\text{i}\right.\)”) represent minor triads. Uppercase Roman numerals with a “\(\left.\text{}{+}\right.\)” are augmented (e.g., “\(\left.\text{III}{+}\right.\)”), and lowercase Roman numerals with a “\(\left.\text{}^{\circ}{}\right.\)” are diminished (e.g., “\(\left.\text{vii}^{\circ}{}\right.\)”). (There is also the Nashville Number System, which uses Arabic numbers for chords instead of Roman numerals.)

Key Lead–Sheet Root Scale Degree of Root Roman Numeral Notes in Chord
\(\text{G}\) \(\left.\text{B}\text{m}\right.\) \(\text{B}\) \(\hat{3}\) \(\left.\text{iii}\right.\) \(\text{B}\)–\(\text{D}\)–\(\text{F}^♯\)
\(\text{f}\) \(\left.\text{G}^{\circ}{}\right.\) \(\text{G}\) \(\hat{2}\) \(\left.\text{ii}^{\circ}{}\right.\) \(\text{G}\)–\(\text{B}^♭\)–\(\text{D}^♭\)
\(\text{c}\) \(\left.\text{E}^♭{}\right.\) \(\text{E}^♭\) \(\hat{3}\) \(\left.\text{III}\right.\) \(\text{E}^♭\)–\(\text{G}\)–\(\text{B}^♭\)

For inversion of Roman numerals, we will use a modified “slash chord” notation until we study Figured Bass later on. For now, we will write “\(\left.\text{I}\right.\)/3rd” if the 3rd of the \(\left.\text{I}\right.\) chord is the bass note, for example.

C: I/3rd means E is the bass note for C-E-G

The following table offers more examples.

Key Roman Num. Root Scale Deg. of Root Notes in Chord Bass Note
\(\text{g}\) \(\left.\text{V}\middle/\text{3rd}\right.\) \(\text{D}\) \(\hat{5}\) \(\text{D}\)–\(\text{F}^♯\)–\(\text{A}\) \(\text{F}^♯\)
\(\text{a}\) \(\left.\text{iv}\middle/\text{5th}\right.\) \(\text{D}\) \(\hat{4}\) \(\text{D}\)–\(\text{F}\)–\(\text{A}\) \(\text{A}\)
\(\text{D}\) \(\left.\text{vii}^{\circ}{}\middle/\text{3rd}\right.\) \(\text{C}^♯\) \(\hat{7}\) \(\text{C}^♯\)–\(\text{E}\)–\(\text{G}\) \(\text{E}\)