FM 880

1.About FM SYNTHESIZER

Frequency modulation synthesis (FM synthesis) is a form of sound synthesis in which a modulator modulates the frequency of a waveform to change its frequency. The frequency of the oscillator varies "according to the amplitude of the modulated signal".

FM synthesis can create both harmonic and inharmonic sounds. To synthesize harmonic sounds, the modulating signal must have a harmonic relationship to the original carrier signal. As the amount of frequency modulation increases, the sound grows progressively complex. Through the use of modulators with frequencies that are non-integer multiples of The carrier signal (i.e., inharmonic), the harmonic bell-like synthesizer can create harmonious and dissonant sounds. In order to synthesize a harmonic sound, the modulating signal must have a harmonic relationship with the original carrier signal. As the amount of frequency modulation increases, the sound becomes more and more complex. By using modulators with frequencies that are non-integer multiples (i.e., non-harmonic) of the carrier signal, a non-harmonic bell and impact spectrum can be created.

Frequency modulation synthesis using analogue oscillators may cause pitch instability. However, FM synthesis can also be achieved digitally, which is more stable and becomes standard practice. Digital FM synthesis (implemented as phase modulation) became the basis for several Musical Instruments as early as 1974. Yamaha built the first prototype digital synthesizer in 1974, based on FM synthesizer, [2] and then in 1980 commercially released the Yamaha GS-1Synclavier I, manufactured by New England Digital Corporation beginning in 1978, including a digital FM synthesizer, used from Yamaha. [4] Licensed FM Synthesis Algorithms Yamaha's breakthrough DX7 synthesizer, released in 1983, brought FM to the forefront of synthesis in the mid-1980s.

2. About FM 880

Let us looking for the product, the FM880 is a synthesizer which is basis in the software system. I use the "purr-data" to develop the user interface. When people using the FM 880, they will use the Micro-Bit to control the synthesizer in the PD( Purr- data). They can use the Micro-bit to send the signal to open the 'dsp' ，which is use to turn on the sound playing, at the same time, I also used the device's built-in accelerator to control many other MIDI parameters, Moreover, this produce has two types os different model of controller. First, you can use the Micro-bit to trigger sound signal, but this requires the user to adjust the pitch parameters on the PD interface. Second, you can assign a pitch to a key and then trigger a preset pitch with a specific key.

Overall, It is a software synthesizer with a unique interactive experience that infuses electronic music performances with new elements and makes them more enjoyable to watch than just what we see as a DJ.

• Micro-bit device https://makecode.microbit.org
• Purr data

Now let me introduce you to the PD interface, this is the main interface of the FM synthesizer I developed with PD. The Region A, located at the top of the picture, is the modulated signal oscillator. At present, I open up the sawtooth and sinusoidal waves as modulating sources. And then, there's region B, the part that's selected by the circle，this is the master signal oscillator，in fact, by observation we will know that both of these oscillators can adjust the frequency. On the far left of the picture, we can see region C，this is a very noteworthy area, as they are actually two "subpatches" that have hidden functions for the user to use. Finally, the synthesizer has a filter and reverb, which I'll talk about later！

BBC Micro: Bit is a microcontroller originally developed by the BBC to teach programming to primary school children as part of a reform of the national IT curriculum. A microcontroller is essentially a very small computer. It has a CPU, RAM, storage in the form of flash memory, and a number of input and output pins that you can connect to other components. It also has two programmable buttons, a 5x5 LED display, a Bluetooth antenna, and a built-in compass and gyroscope to measure acceleration in different directions.

In this practice，this device will be used as a signal trigger, and its accelerator will be used as a signal，The purpose of this is to allow the user to have physical interaction with the driver to change the audio parameters.The accelerator can accept vector signals of X, Y and Z dimensions. However, due to the problem of sensor accuracy, I packaged the signals of these three dimensions in different codes for customers to download. In other words, the customer is temporarily unable to use the three dimensions of the signal at the same time, the user can only download and retrieve them when needed.

As I mentioned earlier，we use key B to trigger the sound signal，after the sound signal is triggered, we can use the accelerator to adjust the audio parameters. When we need to use the Accelerator, we first need to enter the preset command to select the direction of acceleration on the X, Y, and Z axes, which are up and down, forward and backward, and left and right. After the user chooses, they can move the device in the specified direction and implement parameter change，There are two things to note when using it. First, no matter which direction vector information you choose as the control signal data source, you need to hold down the A button while you are moving the device. Second, all parameters can be modified.

After we know how to use the micro-bit, we need to understand the various parameters of the PD interface, As shown in the picture, except for the modules described earlier，this section focuses on the effects module，in the middle of the screen, we'll see an object with "hip ~" written on it，This is a high pass filter，on its right side, there is a slider to adjust the filtering frequency. I also provide a low-pass filter for replacement if the user desires it. Finally is the reverberation, on the right side of the picture, this is also a can choose to use the module, when users need to use, just like the picture it connected to the main module, can be used, however, it is important to note that because the Micro - is the MIDI control signal sent by a bit, so the numerical range is 0 to 127, however, In the reverberation module, all variables are within a range of 10, so you need to be careful to use the accelerator to change the parameters.

Finally, I'd like to discuss the current progress of the FM880 and its prospects for the future，so far, the FM880 has achieved basic synthesizer control. Users can use gestures to complete the real-time control of sound parameters，in fact, users can control the synthesizer with more expressive gestures, this makes the operation of the product more interesting. I would love to see users share their own gestures and make the device a community of users. Although limited by technology and hardware, the FM880 may not be able to achieve completely free gesture setting at present, but this will become one of the directions I will work on in the future.

About its future，I'm going to look for better sensor systems for it, I will continue to develop the function of FM880 on PD，predictably，I'm working on using life as a modulation signal to bring more options to sound design，So, join us!