Introduction to Computer Music: Volume One

1. How does the MIDI system work? Page 11

Compositional Uses of MIDI

MIDI Controllers

Because MIDI instruments were made available in both keyboard and rack-mount module versions, most studios and individuals opted for one keyboard synthesizer controlling an array of tone modules. Many synthesizer keyboards are limited to 61 notes and lack a piano-like feel. To improve upon this, 88-key wooden weighted keyboard controllers, generating MIDI codes but no sound themselves, were introduced as input devices. A prototype keyboard was introduced by Robert Moog, creator of the many generations of Moog synthesizers, which increases the performer's ability to shape notes by sliding fingers forward or backwards and side-to-side on each key, in addition to expressive use of key pressure and velocity. The assignment of controller and/or SysEx codes to these axes is controlled by a programmable PC interface to the keyboard.

Alternative controllers to the MIDI keyboard have developed over the last several years. Gary Nelson, both an electronic composer and tubist developed a controller with a tuba mouthpiece and brass fingerings. Both Yamaha Corporation and Casio have marketed wind controllers with saxophone and/or clarinet fingerings. In both of these instruments, wind pressure generates a Note On command and continues to control the amplitude by converting the pressure into controller information. These controllers require an intervening microprocessor to convert the various fingering combinations into note numbers. MIDI guitars, violins, and drums have become commonplace in the world of commercial music. MIDI drum pads, pedals and many other devices also were marketed as controllers. There are several MIDI body controllers, a series of programmable pads sewn into a leather jumpsuit which the performer plays on, which has done away with the need for an instrument at all. Several wireless sensing devices, such as the Kroonde Gamma have allowed composers to use real-time physical sensors on dancers, etc. which may trigger musical events through conversion to MIDI. Composers such as Sylvia Pengalli have even explored brain waves converted to MIDI data as a compositional device.

The desire to track acoustic instruments or the human voice had led to the development of pitch-to-MIDI converters, such as the famous IVL Pitchrider. Many software packages now include their own internal pitch-to-MIDI conversions. Miller Puckette, a key developer of the interactiveMIDI/audio program MAX/MSP (Cycling '74)has written two extensions called ~fiddle and ~bonk for tracking either string, wind, or percussive sounds. Either a contact mike or standard "air" mike is connected to the converter, which then outputs MIDI note numbers and other programmed parameters, such as volume and pitch bend. Certain problem are inherent in such devices. For example, the converter may fail to track the fundamental pitch of instruments or voices with strong or complex overtones. In addition, they often have difficulty tracking rapid note patterns. However, despite their current limitations, these converters have opened up a new area of interactive performance between instrumentalist and computer in conjunction with some of the software mentioned below.

Finally, video data, either live or captured, is also being converted to MIDI for interactive composing. Early on, composers such as Tom Lopez set up installations with video cameras. The program he wrote checked for changes in pixels, caused for example by someone walking across a lobby. Those changes would then generate MIDI codes. Corrently, Cycling '74 markets a program called Jitter, a companion to MAX/MSP which greatly expands the potential interaction between video, MIDI and audio.

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