Akai MPC Essentials User Manual page 144

MIDI: MIDI stands for musical instrument digital interface. Developed in the early 1980s, MIDI enables
interaction between various types of electronic music instruments from different manufacturers. At the
time a communications standard for heterogeneous devices did not exist, so MIDI was a significant
advance. It made it possible to link various devices with one another through simple, standardized
connectors.
Essentially, this is how MIDI works: One sender is connected to one or several receivers. For instance, if
you want to use a computer to play a MIDI synthesizer, the computer is the sender and the synthesizer
acts as the receiver. With a few exceptions, the majority of MIDI devices are equipped with two or three
ports for this purpose: MIDI In, MIDI Out and in some cases MIDI Thru. The sender transfers data to the
receiver via the MIDI Out jack. Data are sent via a cable to the receiver's MIDI In jack.
MIDI Thru has a special function. It allows the sender to transmit to several receivers. It routes the
incoming signal to the next device without modifying it. Another device is simply connected to this jack,
thus creating a chain through which the sender can address a number of receivers. Of course it is
desirable for the sender to be able to address each device individually. To achieve this, a MIDI channel
message is sent with each MIDI event.
MIDI Channel: This is a very important element of most messages. A receiver can only respond to
incoming messages if its receive channel is set to the same channel as the one the sender is using to
transmit data. Subsequently, the sender can address specific receivers individually. MIDI Channels 1
through 16 are available for this purpose.
MIDI Clock: The MIDI Clock message transmits real-time tempo information to synchronize processes
among several connected devices (e.g., a sound generator's delay time to a MIDI sequencer).
Modulation: A modulation influences or changes a sound-shaping component via a modulation source.
Modulation sources include envelopes, LFOs or MIDI messages. The modulation destination is a sound-
shaping component such as a filter or a VCA.
Note On / Note Off: This is the most important MIDI message. It determines the pitch and velocity of a
generated note. A Note On message will start a note. Its pitch is derived from the note number, which can
range from 0 to 127. The velocity lies between 1 and 127. A velocity value of 0 is equivalent to a Note Off
message.
Normalize: Normalize is a function to raise the level of a sample to its maximum (0 dB) without causing
distortion. This function automatically searches a sample for its maximum level and consequently raises
the entire sample's level until the previously determined maximum level reaches 0 dB. In general this
results in a higher overall volume of the sample.
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