How to proceed

To take advantage of the time setting algorithm you first define sound-object prototypes with topological and metrical properties. For instance, you may want that the beginning of sound-object 'a' always coincides with the end of the preceding object in the sequence. In this case, you should set property ContBeg to "true". (See §3.2) When the tempo is slow, BP2 may not be able to fulfil this condition unless object 'a' or the one(s) preceding its occurrence(s) have property Reloc (see §3.1). In general, given a set of objects and their properties, the time setting of an arbitrary structure may not yield a solution. If so then some constraints should be released or the process should be abandoned. In many cases there is an infinite number of solutions, out of which a finite subset called canonic solutions may be extracted.

When you click button "Play Selection" (or type cmd-p), if button "Display time setting" is not selected in the "Settings" window, then BP2 will handle everything without notice: if there are solutions to the time setting problem it will take the first one it finds. If there are no solutions it will first attempt to release all continuity constraints (ignoring all ContBeg and ContEnd properties), then it will release only overlapping constraints (ignoring OverBeg and OverEnd properties). If still unsuccessful it will release both types of constraints, in which case there is always a solution.

Since the time setting could become slow in very large structures, if you have set a limit to computation time and that limit is exhausted, BP2 will suddenly release all constraints so that an approximate solution is obtained very quickly.

If "Display time setting" is on then BP2 offers you the option to display the timings of objects and perhaps to make decisions on how to solve constraints. You may also select "Show graphics" to display each sequence. If you decide to display all canonic solutions you will be able to decide which one is appropriate. If you select "Step time setting" you will be prompted to make decisions on every sound-object that needs to be modified to fulfil constraints. For instance, if the beginning of a sound-object is overlapped by the end of the preceding object you may be offered, (1) to delay ("shift") that object, (2) to truncate its beginning, (3) to shift the preceding object, and (4) to truncate the end of the preceding object.

When a sequence is completed it appears both in a numeric (in the "Trace" window) and graphic displays while you are prompted to accept or reject it. If you selected "all canonic solutions" and reject the currently displayed solution, BP2 will display all solutions in a loop until you finally accept one of them or abort the procedure.