Guitar
Amplifiers - Guitar amplification is a specialised field, where much commonly
understood theory does not apply, and little theory is published. Technically speaking, a
guitar amplifier has a specific type of non-linear gain at its signal extremes, and a
specialised type of limited frequency response. This article collection has lots of
information on guitar amplifiers.
The Music Yellow Pages
- index of manufacturers, wholesalers, distributors and nationwide retailers for the
music, pro audio, entertainment and lighting industries
The Musical Instrument Digital Interface (MIDI) enables people to
use multimedia computers and electronic musical instruments together. There are actually
three components to MIDI, which are the communications Protocol (language), the Connector
(hardware interface) and a distribution format called Standard MIDI Files.
The MIDI protocol is an entire music description language in binary
form. Each word describing an action of musical performance is assigned a specific binary
code. MIDI codes are like CPU machine language instructions for musical instruments. First
a byte gives the instruction, if there is parameters, they follow the instruction byte
using data bytes. Most typical MIDI control commands are:
Note off event (key, velocity)
Note on event (key, velocity)
Polyphonic key pressure (key, after-touch)
Control change (command address, command value)
Program change (program number)
Channel pressure (after-touch)
Pitch wheel change (value lsb, value msb)
MIDI was designed for keyboards, so many of the actions are
percussion oriented. To sound a note in MIDI language you send a "Note On"
message, and then assign that note a "velocity", which determines how loud it
plays. Other MIDI messages include selecting which instrument to play, mixing and panning
sounds, and controlling various aspects of electronic musical instruments.
According to the MIDI 1.0 Specification, the only approved MIDI
connector is a 5-pin DIN connector. It is certainly possible to send MIDI messages using
other connectors and cables, but it can cause interconnection problems. A major design
goal of MIDI is to prevent any ground loops that might occur with the MIDI cables. This is
done by using a balanced current loop through an opto-isolator and only grounding the MIDI
outputs. The MIDI IN connector is not grounded to the receiver's chassis. When done
correctly, there are no ground loops and no hum or other noises caused by the MIDI setup.
A PC soundcard exports the serial MIDI signal from its UART on two pins of its joystick or
game port. A special cable with electronics in it converts this to the approved MIDI
connector, and is supposed to include the necessary opto-isolator for conversion to the
required balanced current loop (some PC MIDI cables do not do the isolation and grounfing
correctly!).
When MIDI messages are stored on disks, they are commonly saved in
the Standard MIDI file format. The Standard MIDI File (SMF) is a file format used to store
MIDI data (plus some other kinds of data typically needed by a sequencer). The purpose of
MIDI Files is to provide a way of interchanging time-stamped MIDI data between different
programs on the same or different computers. The format was designed to be generic so that
the most important data can be read by all sequencers. The SMF format stores the standard
MIDI messages (ie, status bytes with appropriate data bytes) plus a time-stamp for each
message (ie, a series of bytes that represent how many clock pulses to wait before
"playing" the event). The format also allows saving information about tempo,
time and key signatures, the names of tracks and patterns, and other information typically
needed by a sequencer. One SMF can store information for numerous patterns and tracks so
that any sequencer can preserve these structures when loading the file. A track usually is
analogous to one musical part, such as one instrument. A pattern would be analogous to all
of the musical parts (instruments) for one song.
MIDI Manufacturers Association -
The MMA was formed in 1984 as a "trust" to maintain the MIDI specification as an
open standard. The MMA provides forums for discussion of proposals aimed at improving and
standardizing the capabilities and marketability of MIDI-related products, and provides a
process for adoption and subsequent publication of any enhancements or clarifications
resulting from these activities.
The Midi Archive - MIDI
and other electronic music stuff, patches, software, songs, documents, links
Standard
MIDI Files 1.0 - This document outlines the specification for MIDI Files. The purpose
of MIDI Files is to provide a way of interchanging time-stamped MIDI data between
different programs on the same or different computers.
What is MIDI
- This document is a good introduction to midi, including interface electronics.
DIY MIDI Controllers
using PIC Microcontrollers and Basic Stamps - By combining a PIC microcontroller or
Basic Stamp II with a few passive components it is not difficult to construct your own
knob box, trigger box, or other MIDI input device. A knowledge of electronics may be
required for interfacing to some sensors. Both the Stamp and PIC provide an economical
(under US$100) entry point into the world of alternative MIDI controllers.
ReTurn MIDI Controller system
- Programmable DIY MIDI controller with many functions (eg SysEx, NRPN etc) and its own
Windows setup editor. Not quite free though, preprogrammed MCU with firmware can only be
purchased from author.