·         Notes are referred to by capital letters: C,E,B and so forth.  Sharps and flats are represented conventionally and come after the note they qualify: D#,Gb,A#...

·         Notes expressed in this way are used in two slightly different contexts: as part of a chord symbol - B13, Eb7 and so on - and as specific single notes.

·         To distinguish the two uses, single notes will be expressed in bold face - C#,F,Ab...  Notes from the next octave higher will be qualified with superscript 1, and the next octave with superscript 2 and so on, thus: C Bb E¹ A¹ C² is a voicing of C13.

·         Each note is separated from every other by a specific interval.  Intervals are expressed with respect to the root note as the origin of a major scale.  So the interval from C to A is a sixth (counting C as 1).  Arabic numbers in chord symbols (5, 9, 13 and so on) refer to the interval with respect to the root note.

·         When we need to express chords or note combinations as generalised formulae then we use Roman numerals instead of letters, representing the corresponding intervals.  Thus the scale of C major is C D E F G A B C¹ D¹ E¹... whereas I II III IV V VI VII VIII IX X... refers to any and every major scale.

·         Similarly, the chord of D-9 (D minor ninth) based on the second note in the C major scale is generalised to II-9.

·         Notes expressed in the generalised, Roman numeral format can also be qualified by accidentals in the same way as specific notes.  Thus the chord of F#7 in the context of the key of C is generalised to IV#7.