Analysis/Synthesis of Harmonic Sounds Based on AM/FM Scaling of ..
Let's look at the components.
First, set both Effects to "Thru" so you can hear the harmonic motion is not coming from the Effects. Also turn off Op 3. Note Op 1 has the Square Feedback Type with a Feedback Level of 112, and Op 2 has the Saw Feedback Type with a Feedback Level of 101. They have no Modulators, so the timbre is just a static square wave for Op 1 and sawtooth wave for Op 2. I have them widely detuned from each other for the sound of two poorly tuned oscillators. But when you play the sound, there's no harmonic motion at all. Now turn off Ops 1 & 2 and turn back on Op 3 and play and hold some notes. You'll hear the harmonic motion is coming from the Op 3 & 4 stack. Great - you know from all we've discussed that as the Modulator Level changes from how its Envelope Levels change over time, we change the level or intensity of the harmonics we hear. But wait, look again – the Envelope Level values for our Modulator Op 4 are all 127! There's no change in the Modulation amount over time at all, so how are the harmonics moving all around? As explained above, we've created a 'pair' of two overtones at each harmonic series interval. Because the detune is the minimum value of -1, the frequency difference is so small between the overtone 'pairs' it sounds very similar to phasing or filter sweep.
So now change the Op 4 detune from -1 to Zero and listen to the sound. It's a static, buzzy pulse/saw hybrid timbre. Reset the Op 4 detune back to -1. The harmonic motion comes back. To speed up this effect, change the Op 4 detune to -2 or -3. One thing to note that regardless of what you set for the base detune value, the rate of the effect will speed up with higher note pitches and slow down with lower note pitches. Next, for variations that combine both this Modulator detune trick with Modulator Envelope control for enhanced harmonic motion, along with detuned Operator Stacks using Algorithm 8 for enhanced thick/lush sound as discussed in prior articles -- check out the three "Massive Slow Sweep Pad" series Voices "", "" and "". This detune trick can also create more intense results using greater detune values that will increase the speed of the harmonic motion, especially if used with stacked modulators. For an example of how that can sound, check out the Voice "" that emulates extreme pulse width modulation in the attack of the sound.
Fixed Frequency Sub-Audio Carriers: Another Cool FM Math Quirk
This trick is similar to the prior Carrier/Modulator detuning trick but with some significant differences. When a Carrier Operator has its frequency set to a sub-audio Frequency value, the negative overtone pair phenomenon mentioned above creates something sonically different than when the Carrier and Modulator are both in the usual audio range. In short, this trick allows us to create detuning within our sound that stays constant - no matter what pitch you play up or down the keyboard - unlike the other detuning types described above that increase with higher pitches and decrease with lower pitches. In addition, it also results in a pulsating effect in volume (amplitude) similar to an LFO tremolo or amplitude modulation. To hear what this effect sounds like, reference the Voice "" on Soundmondo and its accompanying video. This Voices uses Algorithm 1:
The three stacked Modulators 2, 3 & 4 are creating our waveform with the Fixed Mode Carrier Op 1 set at 1.000 Hz creating the pulsating chorus/tremolo effect. Play some notes and you'll hear this effect is constant as you play up and down the keyboard. What's happening is that all you are hearing is just the reflected (mirrored) overtone pairs of the waveform created by Ops 2, 3 & 4 and nothing from our Carrier Op 1 because the setting of 1.000 Hz is inaudible. And instead of the frequency of these pairs being offset by the Operator Detune parameter described in the Carrier/Modulator detuning section, with a Fixed Frequency Carrier each overtone pair is instead offset from each other - a fixed amount equal to twice the Frequency setting of the Carrier. When this value is in the low sub-audio range it will create a detuned 'beating' or pulsating effect similar to a cross between a chorus and tremolo. This example has Op 1 Frequency set to the minimum value of 1.000 Hz, so you will hear this 'beating' or pulsating effect at the same 2.000 rate (twice the 1.000 Hz setting) for every note up and down the keyboard. So you can hear hear the 'raw' waveform from the Op 2, 3 & 4 stack- before it is 'reflected' into overtone pairs by Op 1's Fixed frequency. Let's temporarily change to Algorithm 6:
This Algorithm separates out Ops 2, 3 and 4 into their own stack, so you can now hear their 'raw' waveform. Play some notes and you will hear it is the same timbre - but without the pulsating chorus/tremolo Fixed Frequency Carrier effect. It is also lower volume because the Level of Op 2 is 82, not 120 like Op 1.
Now, change from Algorithm 6 back to Algorithm 1 and let's turn this Voice from a plain example into something interesting and useful.
First, turn on the Pitch EG for Op 1 only and play - and hold - a note. You now will hear the speed of the pulsating chorus/tremolo effect begin at a faster speed - and gradually slow down as the note is held. Then when you release the note, it will speed up again as the Pitch EG rate and level settings are changing the Frequency of Op 1. Next turn of Effect 1 to Flanger and Effect 2 to Chorus to thicken up the sound and create a wide stereo spread. Play staccato arpeggio patterns in the right hand over held octaves or chords in the left hand. To experiment in some ring modulator type of inharmonic sounds, try setting the Op 1 Frequency to various values from 30 Hz up to 600 Hz while also turning the Pitch EG off and on for Op 1. To hear a version of this Voice with a square wave timbre, check out "". To hear some very unique examples combining both Fixed Frequency sub-audio Operators and Fixed Frequency audio range Operators, check out "" and "" where I've 'tuned' the harmonicity of the timbre to specific notes in the scale.
Well, there you have it. We hope you all enjoyed the show, but we're sorry now it's time to go...!
I hope you have found this article series informative and helpful in taking away some of the mystery of FM synthesis; foster a better understanding of its versatility and capabilities; and, encourage you to dive on in to create your own sounds. I'll leave you with some additional content on Soundmodo to hear more examples of the wide range of sounds possible with Reface DX. Check out:
Analysis/Synthesis of Harmonic Sounds Based on AM/FM ..
MSP Tutorial 11: Frequency Modulation - Cycling '74
As we pointed out, the continuous control signals have to play a key role in thesynthesis process. The idea of control signals is quite common and its use can beidentified in most of the synthesis techniques. However, the problem of how to produceappropriate control signals remains. There are two "directions" in which wewould like to derive the control signals. During testing, we would like to measure"reference" control signals from real performances and compare them to syntheticcontrol signals. FM synthesis is a good example how problematic this issue can be. Duringsynthesis, as an ultimate goal, we would like to derive our control signals from symbolicdata. If those control signals are closely tied to musical concepts such as amplitude orpitch, then rules to produce those control signals can be derived by hand or by machinelearning techniques. However, if the control signals represent peculiarities of thesynthesis technique (such as with different physical modeling synthesis techniques, thencontrol signals are more difficult to derive. We propose a new technique, which addressesthese requirements.
Max 7 - MSP Synthesis Tutorial 5: Frequency Modulation
When the Yamaha DX7 FM synthesizer appeared in 1983, it took the world by storm—the DX7 was by far world's most successful synthesizer up to that point (and by number of units sold, probably still is!). Although it is now an "ancient" synthesizer, there are still hundreds of thousands of them still in use throughout the world. The DX7 can make a wide variety of sounds, but it is notoriously difficult to learn how to program it. This is because FM is an inherently non-linear synthesis technique, and also because the parameters of synthesis are too hard to manipulate using the buttons and tiny display on the synth. Initially, not only was FM difficult to understand, but it was supremely difficult to edit all the parameters using using the tiny LCD display that is on those old synthesizers. For both of these reasons, to create new voices on the DX7 was beyond the reach of most musicians.