The BOEUF conceptual framework

BOEUF is a conceptual framework for modeling and building orchestras of digital musical instruments. It consists of a classification of modes of collaboration, and a set of components which can be used to enable these modes in digital instruments. We developed this classification after conducting interviews with digital musicians who work in ensembles, as well as literature review of work on digital ensembles and collaborative instruments. The word “boeuf” is french slang for a jam session.

Modes of Collaboration

The modes of collaboration are a categorization which is intended to describe all the ways that musicians collaborate and communicate during performance. This includes interactions which are mediated (i.e. take place through some technology) as well as unmediated interactions (which can occur through being in the same space together.)

We propose that there are three modes of collaboration: Cooperation, Communication, and Organisation

Cooperation Modes

Cooperation describes the ways that musicians coordinate their actions with respect to their instruments. This cooperation can be:

• Independent: Each musician controls their own instrument. For example, when two musicians begin to play their instruments at the same time this is independent cooperation. They are cooperating because they coordinated their musical gestures, but they act only on their own instrument.

• Complementary: Multiple musicians can affect different aspects of the same musical process. For example, when one musician adds effects to a sound generated by another musician.

• Concurrent: Multiple musicians can control the same aspect of the same musical musical process. For example, when two musicians can both control some parameter (e.g. filter cutoff frequency) on the same instrument.

Communication Modes

Communication describes how musicians exchange information which may then influence their actions.

• Awareness: Awareness describes all non-intentional communication. For example being able to see the movements of other musicians.

• Indication: Indications are intentional communicative acts. For example, cueing an entrance. Deliberate nods and glances between musicians may be indications.

• Exchanges: Exchange is the transfer of musical data between musicians. For example, in a digital ensemble on musician might send a sequence of notes to another’s instrument. Or in a jazz ensemble a soloist might use a motif from the previous soloist.

Organisation Modes

Organisation describes the relationships between musicians. Organisation does not directly affect the sound production, but it impacts how the communication and cooperation modes operate.

• Nomination: Nomination is that act of defining the roles of musicians within the group. For example one musician might be the conductor, another might be a soloist.

• Grouping The act of grouping defines a hierarchy of groups of instruments. For example a musician might be in the group “viola players” as well as in the group “string section.”

• Selection Selection is the act of choosing a group or instrument for cooperation or communication. For example, a conductor might gesture to the wind section (thereby selecting them) before cueing their entrance (indication.)

The Boeuf Components

The Boeuf Components are intended as a generic set of components that would be needed to implement the Cooperation and Communication modes described above. Most, but not all, of these are implemented as objects in the bf-pd library. And there are some differences between these conceptual components and their actual implementation in bf-pd.

• Session: A session represents an instance of a group interaction. A session contains a set of instruments and the network of possible interactions between instruments.

In bf-pd the bf-session object is used to join a session.

• Instrument: An instrument represents a bounded set of music-generating processes (i.e. modules) along with a user interface. In instrument may contain parameters, outputs, meters and it can receive and send messages. We presume that each musician in the ensemble is in control of at least one instrument. Thus, in our modeling an instrument often acts as a proxy for the musician.

In bf-pd the bf-instrument object is used to instantiate an instrument.

• Parameter: A parameter is an attribute of an instrument or module that influences its musical production. Parameters can be of various types such as MIDI events, float or integer values, input audio streams, and so on. Parameters can be:
• Set: where the parameter is set to a new value.
• Retrieved: where the current value of the parameter is returned.
• Watched: where the value of the parameter is sent every time the parameter value changes (until the parameter is no longer being watched.)
• Grabbed: where the parameter can only be set by the instrument that has grabbed it.
• Indicated: where a new value may be proposed for the parameter, but the value is not set.

These actions are always accessible to the instrument that owns the parameter, but permission may be needed for other instruments to access another instrument’s parameter. Concurrent access can be managed in different ways. For example, by grabbing a parameter so that only one instrument can access it at a time.

In bf-pd the bf-param object is used to instantiate a parameter. bf-param enables most of these actions, however grabbing is not currently possible.

• Output: An output is a musical attribute that is produced by a module or instrument. Outputs can be of the same types as parameters. Outputs can be retrieved and watched by another instrument.

In bf-pd the bf-output object can be used.

• Meter: A meter is a component of an instrument that is not used in the actual sound production, but rather gives an indication on the activity of the instrument, which can help enable awareness. For example a meter might display the spectrum or loudness of an instrument’s audio output.

In bf-pd each instrument has an activity monitor that displays a simplified spectrum of the instrument’s output. In the collab window a musician can see this meter for all other instruments in the session. (Note: In bf-pd’s collab window, the view of other instruments’ parameters can effectively function as meters.)

• Group: A group is a set of instruments or other groups. Instantiating a group is an act of grouping. Parameters common to all instruments in a group can be grabbed and set simultaneously. Similarly, messages sent to a group should be sent to all members. For example in a poly-instrument orchestra, a group might be all the musicians with the same instrument. A default group of all instruments is always defined, thereby giving access to parameters common to all instruments in the session e.g. tempo or scale.

Note: Groups are not explicitly enabled in the current version of the bf-pd library.

• Module: A module is a component that produces musical data, of audio or control type. It may be composed of several parameters and outputs. Modules have a type, where each instance of the type has the same predefined parameters. This allows modules of the same type to easily exchange parameter settings. For example, a module of type LowPassFilter might have Cutoff Frequency and Q as parameters, whereas a module of type *MidiPattern** would hold an array of MIDI events.

Note: Modules are not explicitly implemented in the current version of the bf-pd library.

• Message: A message can be some text, image, or video sent from one instrument to another instrument or group. Messages can be generic (e.g. Start, Stop, Fade Out), defined per session, or dynamically created.

Note: While many messages are sent between objects in bf-pd, bf-pd does not currently enable arbitrary or user-defined messages.

For more information :

• The BOEUF project
• Paper presenting the framework