Metrical
properties of sound-objects
The
position of an object in relation to time strea
ks
is calculated on the basis of some properties introduced now. We use the names
of properties as per previous publications. These appear more explicitly in
the new BP2 interface.
Property
PivBeg
means that the streak position is the first MIDI message of the object
prototype.
PivEnd
means the last message.
PivCent
means the centre.
PivBegOn
means the first NoteOn.
PivEndOff
the last NoteOff.
PivCentOnOff
means the centre of the time-span interval starting on the first NoteOn and
ending on the last NoteOff.
PivSpec
is a general case in which the time offset between the first MIDI message and
the streak is specified. These properties are explicitly shown in the dialog
Fig.2.
Fig.2 Editing
metrical sound-object properties
Fig.2
shows that the pivot location may either be defined absolutely (in
milliseconds) or as a percentage of the object's duration. In the latter case,
it will be modified according to the current time base of the performance if
the object has properties OkRescale, OkCompress or OkExpand.
OkRescale
means that this object may be expanded or compressed according to the time
base.
FixScale
means it can't.
OkCompress
means it can be compressed,
OkExpand
that it can be expanded. (See explicit representation on Fig.2) Indeed, if
OkRescale is true, then all other properties except FixScale are made true.
The scaling of an object is expressed by the
dilation
ratio
α. If α > 1 then the sound-object is performed slower than its
prototype. The dilation ratio may be confined to a range deemed acceptable for
the sound-object (see Fig.2). Periodical sound-objec
ts
are handled in a different way, see §2.5.
The
value of α may be sent to the MIDI device (before the sound-object is
performed) in case the sound processor is able to make sense of it for
modifying parameters in synthesis algorithms. (Most commercial synths don't.)
The current value of α is encoded logarithmically in range 0.01 to 100,
and the MIDI controller value is
so
that α = 0.01 will yield 0 and α = 100 yields 128. If you want this
value to be passed to the sound processor each time this particular
sound-object is performed, then check "Send dilation ratio to controlle
r".
"Relocate
at will" (
Reloc)
means that the pivot of the object may be located far from the time streak if
necessary. "Never relocate" forces location on the time streak. Relocation
may also be allowed within specific limits (see Fig.2).