Spherical geometry other geometric concepts are defined as in plane geometry, but with straight lines replaced by great circles. Thus, in spherical geometry, angles are defined between great circles, resulting in a spherical trigonometry that differs from ordinary trigonometry in many respects; for example, the sum of the interior angles of a triangle exceeds 180 degrees. Spherical geometry is "not" elliptic geometry, but is rather a "subset" of elliptic geometry. For example, it shares with that geometry the property that a line has no parallels through a given point. Contrast this with Euclidean geometry, in which a line has one parallel through
Blues scale major scale featuring a flat third and seventh degrees (in effect substitutions from Dorian mode) which, "alternating with the normal third and seventh scale degrees are used to create the blues inflection. These 'blue notes' represent the influence of African scales on this music." \override Score.TimeSignature #'stencil = ##f \relative c' { </score> A different and non-formal way of playing the scale is by the use of quarter tones, added to the 3rd and 7th degrees of the minor blues scale. For example, the A minor blues scale with quarter tones is A–B–C–D–E–F–G, where is a half sharp. Also, the