this beat may correspond to the note value specified by the time signature, or to a grouping of such note values. Most commonly, in simple time signatures, the beat is the same as the note value of the signature, but in compound signatures, the beat is usually a dotted note value corresponding to three of the signature's note values. Either way, the next lower note value shorter than the beat is called the subdivision. Examples In the examples below, bold denotes the primary stress of the measure, and italics denote a secondary stress. Syllables such as "and" are frequently used for pulsing in between numbers. Simple: is a simple triple meter time signature that represents three quarter notes (crotchets), usually perceived as three beats. In this case the subdivision would be the eighth note (quaver). It is felt as : one and two and three and ... Compound: Most often, is felt as two beats, each being a dotted quarter note (crotchet), and each containing subdivisions of three eighth notes (quavers). It is felt as : one two three four five six ... (or, if counting dotted-quarter beats, one and a two and a) Tempo giusto While changing the bottom number and keeping the top number fixed only formally changes notation, without changing meaning – , , , and are all three beats to a meter, just noted with eighth notes, quarter notes, half notes, or whole notes – these conventionally imply different performance and different tempi. Conventionally, larger numbers in the bottom correspond to faster tempi and smaller numbers correspond to slower tempi. This convention is known as tempo giusto, and means that the tempo of each note remains in a narrower, "normal" range. For illustration, a quarter note might correspond to 60–120 bpm, a half note to 30–60 bpm, a whole note to 15–30 bpm, and an eighth note to 120–240 bpm; these are not strict, but show an example of "normal" ranges. This convention dates to the Baroque era, when tempo changes were indicated by changing time signature during the piece, rather than by using a single time signature and changing tempo marking. For example, while , , , and have the same beat pattern, they would conventionally be used for increasingly slow music. A 20th century example is "O Fortuna" (1935–1936) by Carl Orff, which begins slowly in , and then speeds up and changes to