MIDI data

MIDI data messages are transmitted serially through a MIDI cable, meaning that 1 bit follows the previous bit. Each message is in an 8-bit word, or byte. With each word, however, the fi rst bit indicates whether it is a “status byte” with a 1, or a “data byte” with a 0. This gives MIDI data a 7-bit resolution, so the true range of MIDI data is a total of 128 points of reso- lution, 0 through 127. What this means is there are 128 play- able notes and 127 velocities, with 0 equivalent to a “note off” command.

Pressing a single key of a MIDI keyboard controller sends three 8-bit messages: note on/channel number, note number, and note on velocity. Releasing the key sends a similar set of three messages: note off/channel number, note number, and note off velocity. In most situations, a note on velocity of 0 is the equivalent of a note off message.

Because of the density of MIDI messages that are sent and received, it is possible for a note message to be “stuck” on. This is fi xed by either pressing the key again to retransmit the note off message, or by pressing a “panic” button featured on most controllers and sequencers. This sends a note off message to every note on every channel of the system and takes a few seconds to complete.

Using Samples

7.1.5 Controllers

The term controller is used in different contexts with regard to MIDI. The controller can be the entire MIDI keyboard. The various faders on knobs on a keyboard can also be referred to as controllers. It is important to note the context in which the term is being used.

MIDI data can also carry control change information. The control knobs and sliders on a MIDI keyboard transmit this control change information. This is one context in which these input devices are referred to as controllers. These con- trollers are used to adjust a particular parameter of an instru- ment. They are merely a different means of inputting MIDI data. Just as there are a total of 128 MIDI note numbers, there are also 128 basic MIDI controllers. Some of these controllers are predefi ned if the device is designated to receive such information. For example, controller #1 is the modulation wheel, which is found on most standard MIDI devices. The modulation wheel sends a 0–127 message when the wheel is moved up or down. It can then be designated in the target MIDI device to adjust a specifi ed parameter, such as fi lter cutoff frequency or volume.

It is important to note that the majority of control change data is sent only when the controller is moved. It does not continu- ously transmit data. For example, if the controller is set in the middle, when the user loads a patch, whatever parameter is being adjusted by the controller is set to its default position according to the patch. However, if the controller is moved slightly up or down, the parameter immediately jumps to the data that the controller is transmitting. This can create an abrupt jump in whatever parameter is being controlled. MIDI keyboard controllers, which have various sliders and knobs, have a default number assignment, which transmits on that previously assigned controller number assignment. This controller number is often adjustable by navigating menus on the controller itself or via editing software on the more advanced MIDI controllers.

Audio Sampling

In the same way that controller numbers are adjustable on the keyboard controllers themselves, the parameters that the user wishes to control can also be adjusted to react to a speci- fi ed controller number. With many software instruments, they can be attached to the controller number by specifying that they be attached to the next controller number message that they receive. Once the controller is moved, the parameter is “learned,” and so this feature is often called MIDI Learn. The controller controls the associated parameter until further changes are made.

Since MIDI sequencers record MIDI data, such as note on, velocity, and note off data, they can also record controller data. It is generally helpful to record the controller data on a different track of the MIDI sequencer, so that the controller’s data can be muted or edited easily. Sequencers allow the user to quantize and edit the MIDI data, and con- troller messages can be edited in the same way. Most sequencers allow controller data to be drawn in with various tools, or even automated as a virtual fader on the sequencer itself.

MIDI has many more capabilities than the basic operations mentioned here, including transmitting time code for syn- chronization and system exclusive messages for storing patches with an editor/librarian. The MIDI standard changes occasionally to incorporate new features as recommended by the MIDI manufacturers, but the basics of transmitting note and controller information have remained the same. It is an open system with room to grow, which is why the format has survived for decades. It can be as simple or as complicated as the user requires.

7.2 Musical instrumentation

Employing sound sampling to assemble the parts or voices of a performance ensemble is an extension of the same chal- lenge faced by musicians for centuries. The musical success of a composition is largely dependent on the choice of voices or instrumentation.

Using Samples

Here are defi nitions of the typical choices for instrumenta- tion.

7.2.1 Emulation

Emulation refers to the performance of sampled sounds as

exact replacements for traditional instruments. The objective is to convince listeners that they are hearing an acoustic per- formance of the same music.

7.2.2 Transcription

Transcription means setting an existing piece of music for a

different ensemble of instruments. The original form is fol- lowed quite closely. The new ensemble can be of acoustic, electronic, or sampled instruments, or any combination. The performance characteristics of the new ensemble should be faithful to the composer’s original intention.

The music stays the same; the ensemble is different.

Listen to Vladimir Ashkenazy’s 1982 orchestral transcrip- tion of Mussorgsky’s “Pictures at an Exhibition.” Compare it with the original piano version performed by Vladimir Ashkenazy.

7.2.3 Realization

Realization means setting an existing piece of music for new

electronic or sampled/processed instruments. It is a form of transcription usually describing electronic orchestration. The music stays the same; the ensemble is of electronic instruments.

Listen to Isao Tomita’s 1975 synthesized electronic realiza- tion of Mussorgsky’s “Pictures at an Exhibition.” Compare it with the original piano version performed by Vladimir Ashkenazy.

7.2.4 Arrangement

An arrangement is a form of transcription that allows for greater fl exibility in modifying the form and instrumentation of the original composition.

Audio Sampling

The music is recognizably the same; the ensemble can be the same or different.

Listen to Emerson, Lake, and Palmer’s 1971 arrangement of Mussorgsky’s “Pictures at an Exhibition.” Compare it with the original piano version performed by Vladimir Ashkenazy.

7.2.5 Composition

Composition means the act of creating a new musical work for

acoustic, electronic, or sampled instruments. A thorough knowledge of the performance characteristics of each voice of the performance ensemble is an integral part of effective composition.

7.3 Composition and orchestration

Eventually you must create a plan and a prescription for the composition to achieve a maximum of ingenuity with a minimum of resources.