ben m
Joined: 15 Sep 2002
Posts: 337
Location: UK |
| Week 8 - MIDI |
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Hi,
ok, we only have 1 week to cover MIDI so it's gonna be coming at you thick and fast this week!
Here goes;
AIDAN
01 - What does MIDI stand for?
05 - Briefly describe the General MIDI standard
09 - What purpose does a MIDI Thru connection serve?
13 - How many MIDI channels are there, and how may more be utilised?
17 - What information is typically found in the data byte?
21 - What is the difference between channel and system messages?
25 - In running status, why is a velocity value of 0 treated as a note off message?
29 - Briefly describe the MIDI TimeCode (MTC) protocol.
33 - Define the term multi-timbral
DANI
02 - Is MIDI a serial or parallel data flow?
06 - What other standards have evolved from GM?
10 - What is daisy-chaining in terms of MIDI connectivity, and what are its disadvantages?
14 - What channel must be used for drums/percussion under the GM standard?
18 - For note on and off messages, what 2 parameters are required?
22 - What MIDI note number is the musical note C3 on a MIDI keyboard?
26 - What is the purpose of the 'Local' setting on MIDI devices?
30 - Briefly describe the MIDI Machine Control (MMC) protocol.
34 - What is aftertouch?
MIKE
03 - How does MIDI data contain timing information?
07 - What is the data rate of MIDI information in kbits?
11 - What are the advantages of multi-port MIDI interfaces?
15 - What does Omni mean in terms of the reception of MIDI information on discrete channels?
19 - What are control change (cc) messages?
23 - How may velocity values are there?
27 - What are system realtime messages?
31 - Why are modulation wheels often found on MIDI keyboards?
35 - What features do mixing consoles offer that can be controlled by MIDI?
NANCY
04 - What are the advantages and disadvantages of MIDI over digital audio?
08 - What is a UART?
12 - What is a MIDI channel?
16 - What is the status byte and what information will it typically include?
20 - What is the purpose of system exclusive (sysex) messages?
24 - What is 'running status'?
28 - What are Song position pointers (SPPs)?
32 - Define the term polyphony.
36 - How do MIDI messages such as modulation, expression attempt to recreate the nuances of 'real instruments'?
Any questions please post them in this thread.
Good Luck.
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ben@audiocourses.com |
Mon Apr 21, 2003 12:07 pm |
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resol69
Joined: 31 Dec 2002
Posts: 69
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Some links to check out:
http://www.harmony-central.com/MIDI/Doc/doc.html
http://www.harmony-central.com/MIDI/Doc/tutorial.html
http://www.borg.com/~jglatt/tech/midispec/
04 - What are the advantages and disadvantages of MIDI over digital audio?
The first advantage is storage space. Data files used to store digitally sampled audio in PCM format (such as .WAV files) tend to be quite large. This is especially true for lengthy musical pieces captured in stereo using high sampling rates. MIDI data files, on the other hand, are extremely small when compared with sampled audio files. For instance, files containing high quality stereo sampled audio require about 10 Mbytes of data per minute of sound, while a typical MIDI sequence might consume less than 10 Kbytes of data per minute of sound. This is because the MIDI file does not contain the sampled audio data, it contains only the instructions needed by a synthesizer to play the sounds. These instructions are in the form of MIDI messages, which instruct the synthesizer which sounds to use, which notes to play, and how loud to play each note. The actual sounds are then generated by the synthesizer.
For computers, the smaller file size also means that less of the PCs bandwidth is utilized in spooling this data out to the peripheral which is generating sound. Other advantages of utilizing MIDI to generate sounds include the ability to easily edit the music, and the ability to change the playback speed and the pitch or key of the sounds independently.
08 - What is a UART?
A UART is a universal asynchronous receiver / transmitter.  Uh, OK, now say that ten times fast.
A UART is present anywhere that a serial bit stream needs to be converted to a parallel byte stream, and vice versa.
The device changes incomming parallel information to serial data which can be sent on a communication line. A second UART can be used to receive the information. This is how info is set to and from a modem for example. You can also use a UART to upgrade from old RS232 designs (those big, clunky connectors with all the pins) to USB. The communications process in a UART is run by registers. If you want to know more about all the registers, click here http://www.lammertbies.nl/comm/info/RS-232_uart.html
12 - What is a MIDI channel?
A MIDI channel is one channel that is usually used to control one instrument. The single physical MIDI Channel is divided into 16 logical channels by the inclusion of a 4 bit Channel number within many of the MIDI messages. A musical instrument keyboard can generally be set to transmit on any one of the sixteen MIDI channels. A MIDI sound source, or sound module, can be set to receive on specific MIDI Channel(s).
16 - What is the status byte and what information will it typically include?
The status byte is the first byte of a MIDI message .It tells you what type of MIDI message this is. Here are the possible values for the high nibble, and what type of Voice Category message each represents:
8 = Note Off
9 = Note On
A = AfterTouch (ie, key pressure)
B = Control Change
C = Program (patch) change
D = Channel Pressure
E = Pitch Wheel
So, for example status of 0x92, we see that its message type is Note On.
20 - What is the purpose of system exclusive (sysex) messages?
MIDI System Messages are classified as being System Common Messages, System Real Time Messages, or System Exclusive Messages. System Common messages are intended for all receivers in the system. System Real Time messages are used for synchronization between clock-based MIDI components. System Exclusive messages include a Manufacturer's Identification (ID) code, and are used to transfer any number of data bytes in a format specified by the referenced manufacturer.
System Exclusive messages may be used to send data such as patch parameters or sample data between MIDI devices. Manufacturers of MIDI equipment may define their own formats for System Exclusive data. Manufacturers are granted unique identification (ID) numbers by the MMA or the JMSC, and the manufacturer ID number is included as part of the System Exclusive message. The manufacturers ID is followed by any number of data bytes, and the data transmission is terminated with the EOX message. Manufacturers are required to publish the details of their System Exclusive data formats, and other manufacturers may freely utilize these formats, provided that they do not alter or utilize the format in a way which conflicts with the original manufacturers specifications.
Certain System Exclusive ID numbers are reserved for special protocols. Among these are the MIDI Sample Dump Standard, which is a System Exclusive data format defined in the MIDI specification for the transmission of sample data between MIDI devices, as well as MIDI Show Control and MIDI Machine Control.
Universal SysEx messages are SysEx messages that are not for any one particular manufacturer, but rather, meant to be utilized by all manufacturer's products. For example, many manufacturers make digital samplers. It became desirable for manufacturers to allow exchange of waveform data between each others' products. So, a standard protocol was developed called MIDI Sample Dump Standard (SDS). There are 2 IDs dedicated to Universal SysEx messages. There's a universal ID meant for realtime messages (ie, ones that need to be responded to immediately), and one for non-realtime (ie, ones which can be processed when the device gets around to it). Here are those ID numbers:
RealTime ID: 0x7F
Non-RealTime ID : 0x7E
24 - What is 'running status'?
Since MIDI data is transmitted serially, it is possible that musical events which originally occurred at the same time and must be sent one at a time in the MIDI data stream may not actually be played at exactly the same time On a given beat, there may be a large number of musical events which should occur simultaneously, and the delays introduced by serialization of this information might be noticeable. To help reduce the amount of data transmitted in the MIDI data stream, a technique called "running status" may be employed.
Running status considers the fact that it is very common for a string of consecutive messages to be of the same message type. For instance, when a chord is played on a keyboard, 10 successive Note On messages may be generated, followed by 10 Note Off messages. When running status is used, a status byte is sent for a message only when the message is not of the same type as the last message sent on the same Channel. The status byte for subsequent messages of the same type may be omitted (only the data bytes are sent for these subsequent messages).
28 - What are Song position pointers (SPPs)?
Master devices that control sequence playback send this message to force a slave device to cue the playback to a certain point in the song/sequence. In other words, this message sets the device's "Song Position". This message doesn't actually start the playback. It just sets up the device to be "ready to play" at a particular point in the song.
32 - Define the term polyphony.
The polyphony of a sound generator refers to its ability to play more than one note at a time. Polyphony is generally measured or specified as a number of notes or voices. Most of the early music synthesizers were monophonic, meaning that they could only play one note at a time. If you pressed five keys simultaneously on the keyboard of a monophonic synthesizer, you would only hear one note. Pressing five keys on the keyboard of a synthesizer which was polyphonic with four voices of polyphony would, in general, produce four notes. If the keyboard had more voices (many modern sound modules have 16, 24, or 32 note polyphony), then you would hear all five of the notes.
36 - How do MIDI messages such as modulation, expression attempt to recreate the nuances of 'real instruments'?
Modulation can be used to create a vibrato affect and expression can add crescendos and decrescendos. This give you a little more manual control over the sound, making the it mimic a real instrument more closely. |
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Tue Apr 22, 2003 8:42 pm |
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Dani
Joined: 28 Jan 2003
Posts: 35
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02 - Is MIDI a serial or parallel data flow?
MIDI is a serial data flow system. You need one cable for MIDI out and a seperate cable for MIDI in.
06 - What other standards have evolved from GM?
GM2, GS (Roland) and XG (Yamaha) are all standards based on General MIDI.
10 - What is daisy-chaining in terms of MIDI connectivity, and what are its disadvantages?
Daisy chaining is the ablility to chain together several MIDI instruments so that you can use more than one sound source at once. A musician can build a sound using different instruments and play sounds back simultaneously using one keyboard or sequencer. Or you can use a bass sound from one sound source, drums from another and strings from a third. The advantage to this is each sound can be mixed in live from the soundsource and mixed/eq'd independently, which saves tracks.
The disadvantage of daisychaining is that it can be a complex operation to set up different sound sources to react to only the MIDI data that is specifically for that instrument and also, there can be problems with latency if the chain is too long.
14 - What channel must be used for drums/percussion under the GM standard?
MIDI channel 10 is the channel used by General MIDI for drums. Although, you can assigne a drum kit to any MIDI channel if needs be.
18 - For note on and off messages, what 2 parameters are required?
Key Number and MIDI channel.
22 - What MIDI note number is the musical note C3 on a MIDI keyboard?
144 60 64
26 - What is the purpose of the 'Local' setting on MIDI devices?
The local setting enables the keyboard to play the soundsource built into it. Mostly used when the keyboard hasn't got MIDI plugged into it, or it doesn't recieve a MIDI thru signal from another device.
If you have a MIDI Synth plugged into a sequencer and the sequencer has MIDI thru enabled, then note information is passed through it back to the keyboard, which of course with LOCAL ON, would mean that the note would play twice. This makes drum sounds sound like they are flamming.
3
0 - Briefly describe the MIDI Machine Control (MMC) protocol.
MIDI Machine Control (MMC) is a protocol specifically designed to remotely control hard disk recording systems, and other machines used for record or playback, over a MIDI cable. The only way to do this is with System Exclusive messages, and so several specific SysEx messages were defined in order to implement MIDI Machine Control. Many devices support this protocol (although a more elaborate protocol was later created called MIDI Show Control, which features a command set to control non-musical equipment such as lights and effects devices).
http://www.borg.com/~jglatt/tech/mmc.htm
34 - What is aftertouch?
Aftertouch is the ablility of a keyboard to produce expression by pressing harder on the keyboard after the note has been triggered. Mainly used for modulation effects but can also be used to change just about any parameter on a modern synth. There are two flavours of aftertouch, MONO aftertouch which affects every note by pressing one key harder and polyphonic aftertouch which affects on the note that is being pressed harder. Most synth users used top block aftertouch information as it takes up a lot of memory (back in the days of small hardware sequencers) also, you can inadvertently modulate the sound when you don't want to. |
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Thu Apr 24, 2003 8:51 am |
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MIKE_NOSTRADAMUS
Joined: 08 Jan 2003
Posts: 163
Location: Northfork Recording Studios |
| mike's answers |
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Hi I’m back for how long I’m not sure here’s what I got so far!!!I’ll edit this when I return to complete.
Mike
AIDAN
01 - What does MIDI stand for?
Musical instrument digital interface(human to machine translator throught numbers
05 - Briefly describe the General MIDI standard
a number of companies got toghether in the late 70’s to come come up with a standard so all midi instruments could communicate with one another .this worked up to a certain point .some still had to be reprogramed to recognized another companiy’s language.
09 - What purpose does a MIDI Thru connection serve?
Its another out connection to serve as daisy chaining up to 5 or 6 midi components.better have good cables for this because weird things can happen here.
13 - How many MIDI channels are there, and how may more be utilised?
There are 16 channels and that’s it on GM..Todays units can handle up to 32 channels
17 - What information is typically found in the data byte?
Volume,tempo,sustain.voice,key velocity
Note on/note off
21 - What is the difference between channel and system messages?
25 - In running status, why is a velocity value of 0 treated as a note off message?
29 - Briefly describe the MIDI TimeCode (MTC) protocol.
33 - Define the term multi-timbral
A sampler or module that can play several parts at the same time,each under the control of a different midi channel
DANI
02 - Is MIDI a serial or parallel data flow?
06 - What other standards have evolved from GM?
Xg –yamaha and Gs Roland
10 - What is daisy-chaining in terms of MIDI connectivity, and what are its disadvantages?
14 - What channel must be used for drums/percussion under the GM standard?
You can use 10 or 16
18 - For note on and off messages, what 2 parameters are required?
22 - What MIDI note number is the musical note C3 on a MIDI keyboard?
26 - What is the purpose of the 'Local' setting on MIDI devices?
30 - Briefly describe the MIDI Machine Control (MMC) protocol.
34 - What is aftertouch?
MIKE
03 - How does MIDI data contain timing information?
07 - What is the data rate of MIDI information in kbits?
Its bandwidth is 31.25kbaudjust barely high enough to handle multi track without choking
11 - What are the advantages of multi-port MIDI interfaces?
You can increase you channel capabilities.ie. if you use a dual platformmidi interface you can have up to 64 channels 16 midi channels x 4 cables = 64 channels total.you can stack as high as 256 channels but you’ll probably never use them all
15 - What does Omni mean in terms of the reception of MIDI information on discrete channels?
This is where data on all channels is recognized
19 - What are control change (cc) messages?
23 - How may velocity values are there?
27 - What are system realtime messages?
The MIDI System Real Time messages are used to synchronize all of the MIDI clock-based equipment within a system, such as sequencers and drum machines. Most of the System Real Time messages are normally ignored by keyboard instruments and synthesizers. To help ensure accurate timing, System Real Time messages are given priority over other messages, and these single-byte messages may occur anywhere in the data stream (a Real Time message may appear between the status byte and data byte of some other MIDI message).
The System Real Time messages are the Timing Clock, Start, Continue, Stop, Active Sensing, and the System Reset message. The Timing Clock message is the master clock which sets the tempo for playback of a sequence. The Timing Clock message is sent 24 times per quarter note. The Start, Continue, and Stop messages are used to control playback of the sequence.
31 - Why are modulation wheels often found on MIDI keyboards?
To change the pitch of the voice
35 - What features do mixing consoles offer that can be controlled by MIDI?
NANCY
04 - What are the advantages and disadvantages of MIDI over digital audio?
08 - What is a UART?
12 - What is a MIDI channel?
16 - What is the status byte and what information will it typically include?
20 - What is the purpose of system exclusive (sysex) messages?
24 - What is 'running status'?
28 - What are Song position pointers (SPPs)?
32 - Define the term polyphony.
36 - How do MIDI messages such as modulation, expression attempt to recreate the nuances of 'real instruments'?
Any questions please post them in this thread.
Good Luck.
Last edited by MIKE_NOSTRADAMUS on Fri Apr 25, 2003 12:36 pm; edited 1 time in total |
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Thu Apr 24, 2003 12:36 pm |
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Aidan
Joined: 08 Jan 2003
Posts: 38
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1.What does MIDI stand for?
Musical Instrument Digital Interface-a system developed to allow the communication between different musical instruments digitally.
5.Briefly describe the General MIDI standard.
The General MIDI Standard is a bank of 128 sounds that ensures nominal sound compatibility between instruments of different makes.It was developed to enable manufacturers to build synthesisers & synth modules that exhibited a specified degree of compatibility in terms of which sounds were located in which patches,to which keys the various drum sounds were mapped and on the minimum performance capability of the machine in terms of multi-timbrality and polyphony.The aim is to allow a MIDI sequencer recorded on a GM module to be played back on any other GM module without needing to repatch anything.
9.What purpose does a MIDI thru connection serve?
It sends a copy of the MIDI In signal allowing several MIDI instruments to be linked together .It allows the signal to pass through the unit and on to the next unit and so on.
13.How many MIDI channels are there,and how may more be utilised?
There are 16 MIDI channels-the information can be sent to anyone of the 16 channels.If you use a multiport MIDI interface in conjunction with compatible sequencing software you can have several different sets of 16 MIDI channels.The ports can be designated by number or letter to give say 16 channels on Port A,16 channels on Port B etc.By connecting a different 16 part multi-timbral synth module to each port of a 4 Port Interface you can have 64 different sound sources each of which can be individually addressed.
17.What information is typically found in the data byte?
Key numbers- indicating which key was pressed and velocity-how hard the key was pressed.It may also include Pitch bend details and program specific numbers.
21.What is the difference between channel and system messages?
Most MIDI messages are channel specific in that they are only accepted by the receiving device if that device is set to same channel on which data is being sent. MIDI note on and offs ,performance data such as velocity,pitch bend,controller data and program changes are all channel messages.
System exclusive or SYSEX messages are part of the MIDI system message portfolio but system messages are provided so that manufacturers can build instruments with different facilities yet still conform to MIDI specifications.These messages are only recognised by the type of instrument for which they are designed.
25. In running status,why is a velocity value of 0 treated as a note off message?
Running status is used to help reduce the amount of data transmitted in the MIDI data stream.It considers the fact that it is common for a string of consecutive messages to be of the same type,eg. a chord may contain 10 successive Note On messages followed by 10 successive Note Off messages If running status is used a status byte is only sent when the message is not of the same type as the last message on the same channel.The effectiveness of running status can be enhanced by sending Note On messages with a velocity of 0 in place of Note Off messages-resulting in long strings of Note On messages.
29.Briefly describe the MIDI timecode(MTC) protocol.
MTC is MIDI Time Code and is a MIDI sync process based on SMPTE time code. Its independent of musical tempo and it gives positional information expressed in hours,minutes,seconds and frames.Its data is shared with other MIDI data and is sent in short bursts.Its best to make sure the port carrying the MTC signal isnt shared with other MIDI data to avoid corruption and delays.
33.Define the term multi-timbral.
Multi timbral means that a sound source is capable of producing several different sounds at the same time. |
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Thu Apr 24, 2003 12:43 pm |
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