In Interval Practice mode, xones are activated by selecting combinations of interval Sizes, Qualities, Types, and Intonations. According to tradition, interval qualities correspond to sizes as follows:

Sizes		Qualities
Perfect	Unison, Fourth, Fifth, Octave	dim. Perfect aug.
Imperfect	Second, Third, Sixth, Seventh	dim. minor Major aug.

Types correspond to members of interval families, and intonations correspond to fine tuning in JND steps. For more information, see the H-System help page.

A Perfect intonation means that the interval does not deviate from its ideal value. As explained on the H-System and Notation help pages, the default interval values considered ideal are those of Just Intonation within the 13-Limit, which may be notated with a natural, sharp or flat inflection, depending on interval size and type. A few perfect intonations of intervals ascending from C are shown in the table below.

Perfect Fourth, P4 = 3:4	Perfect Small Major Third, P.SM3 = 4:5	Perfect Large Minor Third, P.Lm3 = 5:6
C up to F	C up to E	C up to E

Selecting any intonation other than Perfect means that you are testing your ears to identify mistunings of intervals from their ideal values. The surrounding intonations deviate from Perfect in steps of 1 JND.

The initial pitch of an interval is referred to as a Root in XENTONE. You may select the Tonic of the current Key, in which case all intervals begin with 1/1, or you may select a Random root, which may be either completely random, or may be randomly chosen from the currently selected Scale. Note that Root from Scale and Xones from Scale operate independently of each other, so it is possible, for example, to hear Just Intonation intervals on random roots selected from a scale of 5ET. Use the Pedal root selection to tune more intervals on the last randomly chosen root.

There are four possible styles of intervals, referring to combinations of direction and sounding melodic versus harmonic. The placement of the Root depends on the selected direction. When the direction is ascending, the root is the lower tone, and when the direction is descending, the root is the upper tone. For example, an ascending M3 from C will be C up to E, while a descending M3 from C will be C down to A