### Tempo and gaps

If no indication is given, a sequence of symbols is interpreted as "one symbol per time unit". We mean symbolic time units counted on a symbolic tempo. Sound-object sequence "a b c d e f" may also be notated "/1 a b c d", where "/1" is called an explicit tempo marker. Similarly, if the same sequence is to be interpreted three times faster it is notated "/3 a b c d e f".

Using explicit tempo markers makes it possible to change tempo within the string. For instance, in sequence

/2 a b c d e f /3 g h i j k l m n o

'a' ... 'f' are interpreted at speed 2 (two sound-objects per beat) while 'g' to 'o' are interpreted at speed 3. (This may also be viewed as a tempo acceleration of 3/2.) If '_' (empty sound-object) is used to denote a prolongation of the preceding object, the same expression may equivalently be notated:

/6 a_ _ b_ _ c_ _ d_ _ e_ _ f_ _ g_ h_ i_ j_ k_ l_ m_ n_ o_

Gaps (silences or rests) are written as hyphens or integer numbers. The following notations are equivalent:

/2 a b - - c d /3 e - - - - f g h
/2 a b 2 c d /3 e 4 f g h

Rational numbers may also be used to indicate fractional gaps, e.g.

/1 a b /2 c d e f 4/3 g h

in which 'a' and 'b' are interpreted at speed one, 'c', 'd', 'e', 'f', "g" and "h" at speed two while sequences "cdef" and "gh" are separated with a silence of duration 4/3. Since the "4/3" silence occurs at speed two its actual symbolic duration is 4/3 x 1/2 = 2/3. Here again BP2 will expand the representation to

/6 a _ _ _ _ _ b _ _ _ _ _ c _ _ d _ _ e _ _ f _ _ - - - - g _ _ h _ _

where the "4/3" gap is represented as "- - - -" (or "- _ _ _" equivalently). The following representations are equivalent:

/6 a _ _ _ _ _ b _ _ _ _ _ c _ _ d _ _ e _ _ f _ _ - _ _ _ g _ _ h _ _
/6 a _ _ _ _ _ b _ _ _ _ _ c _ _ d _ _ e _ _ f _ _ 4 g _ _ h _ _