Interval number in the context of "Tuning system"

In musical notation, stems are the "thin, vertical lines that are directly connected to the [note] head." Stems may point up or down. Different-pointing stems indicate the voice for polyphonic music written on the same staff. Within one voice, the stems usually point down for notes on the middle line or higher, and up for those below. If the stem points up from a notehead, the stem originates from the right-hand side of the note, but if it points down, it originates from the left. If there are multiple notes beamed together, the stem's direction is defined by the average of the lowest and highest notes in the beam. There is an exception to this rule: if a chord contains a second, the stem runs between the two notes with the higher being placed on the right of the stem and the lower on the left. If the chord contains an odd numbered cluster of notes a second apart (such as C, D, E), the outer two will be on the correct side of the stem, while the middle note will be on the wrong side.

The length of a stem should be that of an octave on the staff, going to either an octave higher or lower than the notehead, depending on which way the stem is pointing. If a note head is on a ledger line more than an octave away from the middle line of a staff, the stem will be elongated to touch the middle line. In any polyphonic music in which two parts are written on the same staff, stems are typically shortened to keep the music visually centered upon the staff.

In Western music theory, a major second (sometimes also called whole tone or a whole step) is a second spanning two semitones (Play). A second is a musical interval encompassing two adjacent staff positions (see Interval number for more details). For example, the interval from C to D is a major second, as the note D lies two semitones above C, and the two notes are notated on adjacent staff positions. Diminished, minor and augmented seconds are notated on adjacent staff positions as well, but consist of a different number of semitones (zero, one, and three).

The major second is the interval that occurs between the first and second degrees of a major scale, the tonic and the supertonic. On a musical keyboard, a major second is the interval between two keys separated by one key, counting white and black keys alike. On a guitar string, it is the interval separated by two frets. In moveable-do solfège, it is the interval between do and re. It is considered a melodic step, as opposed to larger intervals called skips.