#  | ### Under the Hood

Before we start explaining the program a little bit of theory is necessarry to really understand the program. The specifics can be found further on as we explain the instrument editor. The carrier of sound (and thus music) is waves in a medium. On earth the medium is usually air. The vibrations in the air our ear picks up as sounds. Everything which makes sound does so by vibrating the air. Our vocal-chords for instance vibrate the air in elaborate ways to produce speech, a string of a guitar swings too which in turn vibrates the air. The cone of the loudspeaker too vibrates (you can easily verify this by holding your hand near the loudspeaker while playing music) and the way it vibrates is the key to the sound reproduction of Jaytrax.

Jaytrax gives you the control on how the loudspeaker-cone vibrates. You do this by drawing the wave in a Waveform. The shape you draw is the actual movement the cone will make when you play the sound. This movement is repeated indefinately. At this place we shall introduce some terminology. The length of the waveform is called the Wavelength. If you imagine the waveform as the cone vibrating around an axis in the middle you could say that the average fluctuation is perceived as the volume of the sound. If the fluctuations increase, the volume increases. This average fluctuation is also called Amplitude. The nr of waves which are played per second speed is called the Frequency. The faster the waveform is played, the faster the cone vibrates and the higher the perceived tone. See figure 1 for a visualisation of the Wavelength and Amplitude properties of a wave. For the more mathematical under us, there is a direct relation between the wavelength and the frequency. If you halve the wavelength, the frequency will double. This is logical since there are more repetitions of the smaller wave per second, thus the frequency is higher.

### Volume and Panning Control

The control of the amplitude and the frequency in Jaytrax is also done by a waveform. The amplitude of a sound can be modulated by a waveform. The shape of the waveform decides how the amplitude (or volume) of a sound behaves in time. If you look at the waveform in figure 2 you see an example of such an 'AM-Wave' (Amplitude Modulation). Starting from the left you see the wave rapidly decreasing height, than staying at one level for some time and then decreasing untill it reaches the bottom. So, if we use this wave as modulator for the amplitude, the sound would start hard, then decrease swiftly in volume, stay at an intermediate level for some time and then decrease untill you can't hear it any more. With this method you can easily accomodate for any possible volume characteristic for a sound. From swelling strings upto little echoes.

But it doesn't stop here. As most people you probably have 2 ears as well so we would also want to control the balance between the left and right volume. We call this balance the pan. The movement of sound from left to right or vice versa is called panning. The way we control this positioning in the stereo-spectrum is again done by a waveform. As like with the wave which controlled the volume this pan-wave controls the pan-postition. The middle of the wave could be seen as a perfect balance between the left and right volume. If you for instance assign a sine wave as panwave, the sound will gradually go from left to right and back again.

### Frequency Control

So now we have a waveform which controls the volume and we have one which controls the stereo-position. But we still have one charecteristic left out: The Frequency. First of all, the frequency is controlled by the note you play, this is the base frequency. With this base fequency as the center you can increase or decrease the frequency a bit over time. This is done the same way you controlled the pan and the volume, by a waveform. Figure 3 shows an example wave. As you can see the wave is a sinewave which cirles the middle. If you assign this wave as the FM (Frequency Modulation) wave, the frequency will swirl a little around the note you played like a siren. Influencing the frequency like this does so without respect for scales or note-frequencies. There is another method which can change the frequency in time with respect to note-frequencies. This method is called the arpeggiator. An arpeggio is a quick succesion of notes. With an arpeggio you can simulate playing 2 or more notes at the same time with just one instrument (like chords). Last but not least there is a finetune option. The finetune can tune sounds which are off-key with other sounds. You would normally not need the finetune function when you only use the synthesis because they won't be off-key to one another. You could be needing it though when you import sampled sounds, or when you want to tune Jaytrax in respect to other machines which produce sounds, synthesizers for instance.

### Special Effects

The way the waveform looks ultimately decides how it sounds. A wave which resembles a sine sounds really different then a waveform which resembles the tooth of a saw. This is because a waveform is a actually a collection of a lot more basic sinewaves of all different frequencies added up. The unique way all these basic sinewaves of different frequencies are added up is called the timbre. Any conceivable sound is build up this way. What makes interesting sounds is if you could change the timbre while playing the sound. Jaytrax can do this in many unique ways. Again this process is controlled by waves just like the volume and the frequency is.

Most effects consist of a destination wave, one or two source waves an oscillator wave and the effect parameters. In figure 4 you can see an example effect called 'Wavemix'. This effect mixes 2 waves with a given offset to a destination wave. Since the parameters of the sound can be changed in realtime while the sound is playing (or the song for that matter) you can obtain a lot of control over the sound. The dynamic changing of the effect parameters can be done with the aid of the oscillation wave. Again, like before, you can assign one of the waveforms as being the oscillator. This waveform changes one of the effect parameters just like it did the volume or the frequency. All instruments are stackable. This means that any given instrument can use upto 4 effects at the same time. This way really complex sounds can be created.

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