INTRODUCTION TO SYNTHESIZERS - hol.gr

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The slave synthesizer will now also "pass", or "echo" the signal further into the next connected synthesizer via its MIDI Thru jack. The signal will thus travel all the way to the end of the MIDI chain and all connected synthesizers will play the same tone. When you release the key, another MIDI message is created: Release the middle C key. Until this message arrives, the slave synthesizer will keep on playing the note. Here's a little experiment for you to try: depress a key on the master keyboard, and then unplug the MIDI cable before you release the key! What happens? You guessed it - the release command will never arrive to the slave synthesizer, resulting in an endlessly playing tone. This dreaded syndrome is called the "MIDI drone" - pretty scary in a live gig situation! Sometimes the only way to shut off the orphaned tone is to turn the slave synthesizer off and on again. Not just note events, but almost every event that you create on a keyboard will be transmitted like this - pitch bend, after-touch or program change events. Most MIDI commands, such as the Note On commands we looked at so far, can be understood by any synthesizer, regardless of model. You can for instance control a Korg X3 synthesizer from a Kawai K4 synthesizer. But there are also some MIDI commands which are specific for a certain type of synthesizer. These describe the setting of each individual parameter that creates a patch for that synthesizer model. These commands are called "System Exclusive" and are used by synthesizer program editor software. It is impossible to give all the details about every MIDI command in this limited space, so we will not go further into the technical aspects of MIDI. General MIDI The original MIDI standard has some major limitations. We have already bumped into one of them: a MIDI signal doesn't tell us anything about which instrument sound that is supposed to play a specific note. For example, if the composer had selected patch number 5 for channel 1, intending this to be a piano sound, but the synthesizer playing the MIDI data had a tuba sound mapped to patch number 5, then the notes intended for the piano would be played by the tuba - even though this synthesizer may have an excellent piano sound available at some other patch number. To get around this problem, the General MIDI (GM) standard was created. This standard assigns certain memory locations to different families of sounds. Piano sounds are for instance assigned to memory banks 1 - 8, chromatic percussion to 9 - 16, organ-type sounds to 17 - 24 and so on. By using this standard, you can be assured that your string ensemble parts will be played back by a string ensemble sound and not by the 14
accordion or the didgeridoo (even though it may probably sound pretty hilarious). Of course this may not be a problem if you're composing music for your own synthesizer setup, in which case you don't have to bother about where you save your sounds. But if you're composing music for computer games for instance, it's nice to know that your music will sound as intended regardless of which soundcard that will be used for playback, as long as it is GM-compatible. MIDI channels With a little imagination it should be quite obvious, that if we make a chronological list of all the Note On and Note Off commands that make up a musical piece, we have in fact a detailed description on how to play this piece of music on the keyboard. Such a list of MIDI events is usually called a MIDI sequence, and a device or computer software used to record and playback such a sequence is called a MIDI sequencer. But wait a moment: a musical piece usually consists of more than one part - we may for instance have a synthesizer playing a bass part, another synthesizer playing a piano part and a third synthesizer playing a string part. How can we achieve this simultaneous multiple-part playback in a MIDI sequence without all the synthesizers playing the same notes in unison? The answer is, by using different MIDI Channels. Every MIDI command is "tagged" with a channel number from 1 to 16. This means that you can for instance simultaneously send a "C Note On" command on channel 1, an "E Note On" on channel 2 and a "Program Change" command on channel 3. If you have one synthesizer tuned in on channel 1, a second synth on channel 2 and a third on channel 3, then each synthesizer will only respond to incoming MIDI information on their specific channel and ignore everything else. The first synth will thus play the C note, the second synth the E note and the third will perform the requested program change. A MIDI cable can carry information on 16 different MIDI channels at once, which means that we can have 16 synthesizers responding to each of their specific parts. We can record the bass part on channel 1 into a MIDI sequencer, and then overdub the piano part on channel two and the string part on channel three. We can continue until the whole composition is complete or until we reach the 16 channel limitation. When we wish, we can play back all the different channels simultaneously. It will sound just like if we had sixteen musicians playing their synthesizers. Fortunately we don't have to hook up sixteen synthesizers if we want to create a 16-part musical arrangement. Many synthesizers can receive MIDI-data on several different channels at once, just like if they had several separate synthesizers inside their shell. Such synthesizers can for instance play strings, bass, drums and piano at the same time. If you have read the chapter about synthesizer voices, you should remember that the ability to play several different sounds at once is called "multi-timbrality". Sequencing 15
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Page 3 and 4: Pitch The repeat rate of the patter
Page 5 and 6: more "rounded". The more overtones
Page 7 and 8: Of course not just the loudness of
Page 9 and 10: assign it to the new note. One soun
Page 11 and 12: The illustration above shows a simp
Page 13: Sampling is an art - it is very har
Page 17 and 18: By connecting a MIDI-keyboard to th
Page 19 and 20: ... and the Roland D-550 module But
Page 21 and 22: Software-based sequencers are proba
Page 23 and 24: Click on the icon to listen to a mo
Page 25 and 26: The faders The sound volume for eac
Page 27 and 28: pattern. The echoes can be set to e
Page 29 and 30: Sampled or synthetic If you are int
Page 31 and 32: the display for flickering when you

INTRODUCTION TO SYNTHESIZERS - hol.gr

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