ben m
Joined: 15 Sep 2002
Posts: 337
Location: UK |
| Week 5 - Synthesis 2 |
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More questions on synthesis this week.
Here's a few links to help out;
http://www.soundonsound.com/sos/jun00/articles/synthsec.htm
http://www.soundonsound.com/sos/may99/articles/synthsec.htm
http://www.soundonsound.com/sos/apr00/articles/synthsecrets.htm
http://dir.yahoo.com/Entertainment/Music/Instruments/Electronic/Synthesizers_and_Samplers/Synthesis_Types/
http://www.sonicspot.com/guide/synthesistypes.html
http://www.wordiq.com/definition/Synthesizer
Good Luck
a) Which method of additive synthesis had widespread commercial success in the 1980s?
b) Describe the basic principles of this method of synthesis.
c) How this was implemented in the synthesisers that were commercially available.
What are the ADSR characteristics of the following instruments;
Piano
Guitar
Snare Drum
Violin
Describe the effect of the following modulations:
a) A VCO is going into a VCF and to a VCA. The VCO is being modulated by another VCO producing a square wave with a frequency of 15 Hz.
b) A VCO is going into a VCF and to a VCA. The VCF is being modulated by an ADSR.
c) A VCO is going into a VCF and to a VCA. The VCA is being modulated by another VCO producing a sine wave with a frequency of 10 Hz.
In early analogue subtractive synthesis, describe the difference between a voltage controlled oscillator and a conventional oscillator.
In subtractive synthesis, describe the function of the resonance control in a low-pass filter.
Describe three common ways an LFO might be used in analogue synthesis. Include references to other components of analogue synthesisers. Do not use abbreviations in your answer.
Give four terms used in FM (Frequency Modulation) synthesis and not in analogue synthesis.
Describe the waveform source in a wavetable synthesiser.
What technical problem would you expect to encounter when using an old analogue synthesizer for a lengthy live performance, even if the synthesizer is working to its original specifications?
What would be the effect of modulating the VCF of an analogue synthesizer with the LFO?
On the ADSR of an analogue synthesizer, how would you make a note decay to complete silence, no matter how long the key is pressed?
In an FM synthesizer, how would you quickly make a major (but probably random) change in the sound produced?
In an FM synthesizer, what would you adjust to change the high frequency content of a sound?
Which would you expect to sound best on an FM synthesizer: a tinkly electric piano sound or an imitation of string instruments?
Describe how frequency modulation can be achieved with a traditional analogue synthesizer, or modern equivalent. How will the end result differ compared to an FM synthesizer? |
Mon Oct 04, 2004 4:08 pm |
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Rico1210
Joined: 03 Aug 2004
Posts: 39
Location: Newcastle, UK |
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Hi,
here are my questions for this week, i found them really hard this week and i'm not sure about some of my answers.
a) Which method of additive synthesis had widespread commercial success in the 1980s?
In the 1980s, the method of additive synthesis that had widespread commercial success was FM synthesis.
b) Describe the basic principles of this method of synthesis.
FM synthesis (Frequency Modulation) is a form of additive synthesis that uses multiple sine waves (operators) to create an output. This is achieved by using one waveform to modulate another waveform. The original (carrier) signals frequency is oscillated by another signal (modulator) which produces the output. An output can be achieved by modulating the carrier signal with lots of signals (modulators). This complex set of instructions is called an Algorithm. The last signal in an Algorithm is the carrier signal, with all other signals being modulators.
c) How this was implemented in the synthesisers that were commercially available.
The FM synthesizer market was dominated by the Yamaha DX series, in particular the DX7. The DX7 has a total of six operators which together form an algorithm. There are 32 preprogrammed algorithms which are displayed along the top of the control panel.
What are the ADSR characteristics of the following instruments;
Piano - Attack would be zero (fast attack), slow decay, no sustain, fast release
Guitar - Fast attack, instant decay, no sustain or release.
Snare Drum - Attack would be zero (fast attack), instant decay, there would be no sustain or release
Violin - Slow attack, no decay, long sustain (high), fast release
Describe the effect of the following modulations:
a) A VCO is going into a VCF and to a VCA. The VCO is being modulated by another VCO producing a square wave with a frequency of 15 Hz.
The pitch of the oscillator will go up and down sharply 15 times a second.
b) A VCO is going into a VCF and to a VCA. The VCF is being modulated by an ADSR.
The VCF will filter frequencies according to the ADSR envelope
c) A VCO is going into a VCF and to a VCA. The VCA is being modulated by another VCO producing a sine wave with a frequency of 10 Hz.
Changing the amplitude will cause a tremolo effect.
In early analogue subtractive synthesis, describe the difference between a voltage controlled oscillator and a conventional oscillator.
In subtractive synthesis, a Voltage Controlled Oscillator (VCO) changes its frequency according to its input voltage. A conventional oscillator has a fixed frequency, which can be changed but is not dependant on voltage.
In subtractive synthesis, describe the function of the resonance control in a low-pass filter.
Low-Pass Filters(LPF) allow lower frequencies to pass through unaffected and at the same time filters out higher frequencies. This is controlled by Cut Off. The function of the resonance control of an LPF in subtractive synthesis, is to boost the frequencies at the Cut Off point. The higher the resonance, the more the output is filtered. The lower the resonance, the more sound will pass through unaffected. When too much resonance is applied, the frequencies around the Cut-Off are so pronounced that the filter will itself start to oscillate.
Describe three common ways an LFO might be used in analogue synthesis. Include references to other components of analogue synthesisers. Do not use abbreviations in your answer.
The Low Frequency Oscillator can be routed to voltage controlled oscillator to modulate the pitch. This is known as a vibrato effect.
The Low Frequency Oscillator can be routed to voltage controlled amplifier to modulate the amplitude. This is known as a tremolo effect.
The Low Frequency Oscillator can be routed to voltage controlled filter to modulate the cut off frequency.
Give four terms used in FM (Frequency Modulation) synthesis and not in analogue synthesis.
Four terms used in FM synthesis and not analogue synthesis are: Operator, Carrier, Modulator, Algorithm.
Describe the waveform source in a wavetable synthesiser.
Waveform sources in a wavetable synthesizer are generated from a table of pre-set algorithms.
What technical problem would you expect to encounter when using an old analogue synthesizer for a lengthy live performance, even if the synthesizer is working to its original specifications?
The technical problem that would be encountered when using an analogue synthesizer for a lengthy live performance would be the tuning of notes. The notes may go out of tune due to the heat generated.
What would be the effect of modulating the VCF of an analogue synthesizer with the LFO?
Modulating the VCF of an analogue synthesizer with the LFO will cause the filter cut-off frequency to be changed at the same rate as the LFO.
On the ADSR of an analogue synthesizer, how would you make a note decay to complete silence, no matter how long the key is pressed?
To make a note decay to complete silence, no matter how long the key is pressed can be achieved by setting no sustain level. The note will release long or short depending on the set level.
In an FM synthesizer, how would you quickly make a major (but probably random) change in the sound produced?
A quick major change in sound in an FM synthesizer could be achieved by changing the selected algorithm.
In an FM synthesizer, what would you adjust to change the high frequency content of a sound?
To adjust the high frequency content of a sound the frequency of the modulator could be changed.
Which would you expect to sound best on an FM synthesizer: a tinkly electric piano sound or an imitation of string instruments?
A tinkly electric piano sound would sound best on an FM synthesizer.
Describe how frequency modulation can be achieved with a traditional analogue synthesizer, or modern equivalent. How will the end result differ compared to an FM synthesizer?
Frequency modulation can be achieved on a analogue synthesizer by way of cross-modulation. Audio signals can be used to modulate each other. The output of one oscillator can be fed into the control input of another oscillator, as the modulation level of the second oscillators input is increased the sound will change. However, this will not work across the whole keyboard as the tuning may disintegrate. |
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Sat Oct 09, 2004 8:18 am |
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seanm
Joined: 06 Sep 2004
Posts: 20
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| week 5 synthesis 2 |
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hi Ben
here's my answers to synthesis 2
Week 5 - Synthesis 2 - Forums - Classroom 2 - Music Technology 02 2004
a) Which method of additive synthesis had widespread commercial success in the 1980s?
FM synthesis e.g. the ubiquitous Yamaha DX7
b) Describe the basic principles of this method of synthesis.
Commonly at least two sine waves are used. Rather than simply mix the two waveforms, one, the “carrier” is modulated by another, the “modulator”. The interaction of these two sine waves produces multiple frequencies (side bands) and complex timbres, which are based on the sum and the difference of the original frequencies. The greater the modulation depth, the louder these new frequencies are in relation to the original carrier frequency. This carrier can then be modulated further or be used as a modulator for another carrier. The result being that a large number of frequencies can be built up either in a harmonically related series or an un-harmonically related series.
c) How this was implemented in the synthesisers that were commercially available.
FM synthesisers had preset algorithms linking operators together either in series or parallel. Each operator being a sine wave generator (oscillator) and an envelope shaper. These algorithms were specifically designed to influence the routing choices within fm synthesis to deliberately produce the most “musical” results.
What are the ADSR characteristics of the following instruments;
Piano
Fast attack, fast decay, variable sustain (using sustain pedal), if the key is held slow release, if the key is de-activated a faster release.
Guitar
Fast attack, short decay, long sustain, short release.
Snare Drum
Fast attack, short decay, very small sustain, no release.
Violin
Bowed-Slow attack, no decay, long sustain with a slightly faster release.
Describe the effect of the following modulations:
a) A VCO is going into a VCF and to a VCA. The VCO is being modulated by another VCO producing a square wave with a frequency of 15 Hz.
Trilling
The square wave is oscillating 15 times a second modulating the pitch of the first VCO. This will produce two alternate pitches “trilling 15 times a second.
b) A VCO is going into a VCF and to a VCA. The VCF is being modulated by an ADSR.
Change in timbre (harmonics of the waveform). The VCF’s threshold will change in accordance with the envelope set. As the VCF produces timbre this will change over the duration of the envelope set.
c) A VCO is going into a VCF and to a VCA. The VCA is being modulated by another VCO producing a sine wave with a frequency of 10 Hz.
Tremolo. The sine wave is oscillating 10 times a second. The VCA controls the amplitude of the first VCO. The sine wave will cause the amplitude to vary 10 times a second producing a tremolo effect.
In early analogue subtractive synthesis, describe the difference between a voltage controlled oscillator and a conventional oscillator.
Voltage controlled oscillators rely on electrical charges to create waveforms. With Digital Controlled oscillators waveforms are created by digital components. A DCO (digital controlled oscillator or numerically controlled oscillator) contains a “sampled” waveform stored as a series of numbers, a clock oscillator reads these numbers at a speed determined by it’s frequency.
In subtractive synthesis, describe the function of the resonance control in a low-pass filter.
In a low pass filter the resonance control boosts those frequencies bordering the cut off frequency.
Describe three common ways an LFO might be used in analogue synthesis. Include references to other components of analogue synthesisers. Do not use abbreviations in your answer.
A low frequency modulator or LFO generates a variable waveform inaudible to humans but useful as a modulating signal, indeed sometimes though rarely it is called a “modulation generator”. The modulation which it produces simply repeats itself. It can be used to;
modulate the frequency of a voltage controlled oscillator,
modulate the level of the signal via the voltage controlled amplifier,
modulate the frequency content of the signal via the voltage controlled filter,
Give four terms used in FM (Frequency Modulation) synthesis and not in analogue synthesis.
Operator
Carrier
Modulator
Algorithm
Describe the waveform source in a wavetable synthesiser.
Wavetable synthesis involves the “sampled” sound of an existing instrument. These sampled sounds can be stored in wavetables within digital synthesisers. These sounds can then be replayed on demand. This is a sample based synthesis where a variety of techniques such as looping, pitch shifting, mathematical interpolation and polyphonic digital filtering reduces the amount of memory required to store the sound samples. This is because the sampled instruments contain the attack portion a sustain portion (which is looped and as such often only a short portion of the sampled instrument) and a release portion. All of which are stored as separate samples.
More advanced wavetable synthesisers contain waves or tones stored in the same manner intended to emulate existing instruments or create totally new sounds
What technical problem would you expect to encounter when using an old analogue synthesizer for a lengthy live performance, even if the synthesizer is working to its original specifications?
The Oscillators’ pitch(s) has a tendency to drift over time. Therefore the synthesiser will go progressively out of tune.
What would be the effect of modulating the VCF of an analogue synthesizer with the LFO?
The harmonics (timbre) of the waveform will change in accordance with the frequency of the LFO producing an autoWah effect.
On the ADSR of an analogue synthesizer, how would you make a note decay to complete silence, no matter how long the key is pressed?
Set the sustain and release to zero.
In an FM synthesizer, how would you quickly make a major (but probably random) change in the sound produced?
Change the algorithm.
In an FM synthesizer, what would you adjust to change the high frequency content of a sound?
Adjust the parameters of one operator.
Which would you expect to sound best on an FM synthesizer: Tinkly electric piano sound or an imitation of string instruments?
Tinkly electric piano sound.
Describe how frequency modulation can be achieved with a traditional analogue synthesizer, or modern equivalent. How will the end result differ compared to an FM synthesizer?
Use an LFO to modulate the pitch of a VCO. At high frequencies (20Hz and more) the different frequencies of the VCO and LFO will cause pitch modulation. However because the LFO and the VCO are taking their respective pitches from the keyboard, each note pressed will produce a different pitch modulation, causing the two frequencies to change. |
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Sun Oct 10, 2004 5:41 pm |
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