To allow the production of MIDI files, type cmd-option space or select "Settings" in the "Windows" menu. Then check button "Write MIDI files". Whenever "Produce items" (cmd-r) or "Play selection" (cmd-p) are invoked, you are now offered to save the item to a MIDI file. The first time BP2 will prompt the creation of a MIDI file. Then it will propose to create a new file or go on saving to the current one. These are the default file saving options which can be modified in a dialog displayed with "Settings" (cmd-option space), see Fig.33.

BP2 supports three MIDI file formats: types 0, 1 and 2. Here are the tips for choosing an output format:

• If the file will contain a single musical item, or a sequence of items produced by a grammar in the "Improvize" mode, any format is OK. Keep in mind, however, that format 2 may be rejected by single-track MIDI programs.

• In the current version, BP2 saves each item to a single track. Types 0 and 1 may therefore be considered equivalent.

• If the file will contain several independent musical items (each of which might have a different tempo or time signature), then type 2 must be used.

MIDI files may also be imported by sound-object prototypes (see §2.3.1).