CRONOGRAMA DEL CUMPLIMIENTO DEL PLAN DE MANEJO AMBIENTAL

Another common tool that is available when using multiple zones is the alternate or round-robin function. When two or more zones are layered on top of each other with matching velocity ranges, the sounds can be layered together or played in sequence with a different sample being triggered each time a note is played.

This is appropriate when striving for a natural and organic instrument. When a real source is played, there are often dif- ferences in the sound each time it is played, even when the volume is identical. Samplers that lack the round-robin func- tion can often be identifi ed by a listener because of the con- sistency from note to note. An example of this is sampled drums. If the exact same snare drum sample is repeated over and over, it sounds very repetitive and robotic. Each note triggered is exactly the same. Using an alternate sample (Figure 6.10) function, there is more variety and less repeti- tion. Over time, the samples are repeated in a less obvious manner.

6.1.5 Looping

A universal feature that samplers offer is looping. The looping ability of most samplers is limited to several types (Figure 6.11). The loop points determine the start and the end of a

Creating the Instrument

Figure 6.10 Alternate Samples.

Figure 6.11 Looping Options.

section of the sample that is looped. The loop parameter determines the direction in which the looping takes place. • Forward loop: The sample plays from the beginning of the

audio fi le, past the loop start until it reaches the loop end point. It then returns to the loop start point and repeats the looped section until the key is released.

• Alternate loop: The sample plays from the beginning of the audio fi le past the loop start, until it reaches the loop end point. It immediately plays backward from that point to the loop start point. Once it reaches the start point, it plays forward and backward between the points until the key is released.

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Samplers are also capable of reversing the basic playback direction of the sample. This means that a sample can be played back forward (as it was recorded) or it can be reversed. Switching the playback direction of the sample does not change the basic looping functions, although switching the playback direction and looping it does give you expanded options.

The key to successful looping is to create a seamless transi- tion between the start and end of the loop. When a sample has a change in dynamics over time, it is diffi cult to loop because the loop point will have an obvious difference between the beginning and the end. The reversed loop can be a solution for this, but often it seems like the sound is pulsing louder and softer. If that is the desired result, then that is okay as well. If you want a loop that seems to sustain with no obvious loop, then place the start and end points along a section of the sample that has as consistent a level as possible. Also, be aware that any change in pitch will be more obvious when looped. If there is a change in pitch, then the reversed loop might sound like a thick vibrato, but the forward loop will not usually produce acceptable results. Another way to create seamless looping is through the use of cross-fades. At the point where the sample is looped, the audio can be set to cross-fade between the end of the loop and the beginning of the loop. This is extremely useful when you want to create smooth loops but are having a hard time fi nding good loop points.

When setting loop points, there are two general methods. One is to create a very short loop. This might be the length of a single cycle. The other is to use a longer section in the loop. The source will determine which of these is appropri- ate, but both are valid options. It is recommended that you try both shorter and longer loops (Figure 6.12) to discover which is better for your specifi c use. You will fi nd that shorter loops have a very repetitive sound and longer loops are more organic and often more natural.

Creating the Instrument

An important sampler feature is the ability to audition loop points and hear how they sound. A sampler might have no graphic display, so listening would be the only thing you can do in that case. If you hear an audible click at the loop point, it is most likely due to the waveform not lining up properly at a zero crossing. If the sampler has the ability to snap to the zero point along the waveform, then try this and it may fi x the problem. Snapping to the zero point will ensure that the loop ends and starts at the same crossing point level (Figure 6.13).

If you have the ability to see the waveform, then zoom in and set the start and end points so when the loop repeats, the waveform follows the same trajectory. You normally have to audition a few different points until you fi nd one that works. There are often a number of different loop settings that can produce acceptable results.

Figure 6.12 Long vs. Short

Loops.

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6.1.6 Envelopes

An important sampler function that needs to be adjusted during the looping phase is the volume envelope. Volume envelopes have been around longer than samplers and are used in a variety of ways in music technology. The term

envelope refers to the volume of a sound over time and is

divided into four simplifi ed phases: attack, decay, sustain, and release (Figure 6.14). Every sound can be broken into these four phases, although most sounds certainly can be analyzed using many more divisions than four. An envelope

Creating the Instrument

is a tool used by samplers to control the level of sounds, and you can set the attack, decay, sustain, and release (ADSR) of each sample.

The attack is the time from the start of the sound until it reaches its full level. Once that point is reached, there is a period of decay as the sound reaches the sustain level. If the sustain level is the same as the full level, there is no decay. Once the key is released, the sustain phase ends and the sound releases. For zones with no loop points, the sound plays out its length through these zones and no length is added. For zones with activated loop settings, the specifi c loop setting determines whether the loop will continue and fade out during the release phase or whether the loop will end and the remainder of the sample (after the end loop point) will play during the release phase.

The strength of the volume envelope model is its simplicity. Most sounds really do follow these four phases, and synthe- sized sound can be realistic and organic when following the same model. However, the volume envelope model is often oversimplifi ed, in that a sound that is being sustained can often increase in volume to a point that is louder than the fi rst attack. This is not taken into consideration in most enve- lope settings. Some samplers do have additional points along the ADSR envelope, and these can be used to create more complex volume envelopes (for example, A1, D1, A2, D2, S, R).

When an envelope is used to control volume, keep in mind how it affects the other parts of the sampler. A long attack time creates a long fade into the sample, and the initial attack is lost. An attack time of 0 starts the sample immediately with no fade. The decay adds a decrease in volume in addi- tion to any natural decay in the sample. The sustain param- eter affects the level of the sustained section of the sample, including looped sections. The release parameter allows the sample to fi nish past the loop point when the key is released.

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6.2 Advanced mapping

Modern samplers often have advanced mapping features that provide additional realism and creative control. These features are introduced here and there are several tutorials online that demonstrate their full power.

6.2.1 Key switching

There are a few additional features you may want to incor- porate into your instrument, depending on the specifi c sampler you are using. Most of the features discussed so far are universal, but the following features exist in some sam- plers and not in others. Key switching is one of those advanced features. Key switching (Figure 6.15) allows a sampler to respond to a key being pressed, usually in the upper or lower range of the keyboard, which results in a switch between different sample sets. To use this function, you need a full 88-key keyboard or an additional keyboard set in the appro- priate range to trigger the switch. The sample sets can repre- sent just about any instrument, but typically characterize alternate performance styles. An orchestral bank would be a good use of key switching. If you are playing a sampled violin and you want to play staccato and legato in the same phrase without setting up multiple samplers, then a key- switched sample is a possible solution. During playback of the violin sample, you can play the key switch trigger note

Figure 6.15 Key Switching.

Creating the Instrument

and the sampler will switch to a set of staccato sample zones. Once the legato trigger is pressed, the legato zones replace the staccato zones.

Each of the zones, in this example, could have multiple veloc- ity layers and be fully functioning instruments. Key switch- ing can be used in live performance and also to save time and create extremely realistic performances.

6.2.2 Scripting

Another advanced feature offered by a small number of sam- plers is scripting. Scripting consists of a computer program- ming–style language that gives additional control possibilities over the sampler. This ability is used in the creation of super- realistic virtual instruments. The power of this feature can be seen in performance modeling. A script can be used to fi lter incoming MIDI data. A keyboard is normally used to control samplers, but sometimes the instrument that a sampler is re- creating is played in a different way. For example, a violin has four strings, so you can only play four notes at a time (usually only up to two are played simultaneously as a double stop). The specifi c notes that can be played simultaneously are determined by the tunings of the strings and the size of the performer’s hands. When a keyboard controls a sampled violin, however, there is the option to play the violin the same way you play a piano: as many notes can be played simulta- neously as there are fi ngers to play them, and there are no limitations on playing notes that are side by side. This results in a performance that can sound like a string ensemble rather than a solo violin.

A script can be programmed to translate the incoming data from the keyboard into what is physically possible on a violin. If too many notes are played at the same time, then the script can either trigger them naturally or leave some of them off completely. If programmed correctly, a script helps the per- former produce realistic results. It is possible to play a sampler

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realistically without scripting, but it takes more attention to detail on the performer’s part.

Scripting can also create complex performance patches. A common example is a strumming guitar that reacts to specifi c keys being pressed that change the chord being strummed. The style of strumming can be changed as well. Scripting can add a number of additional features to sampling, but it has a steep learning curve. As with all programming, it is no small feat to master the capabilities offered by scripting. There are several examples of sample playback software that utilize systems similar to scripting to create realistic perfor- mance functionality but that cannot be altered by the end user. Many of the available sample players in this category are created by software that allows script programming. The instruments are subsequently packaged into software that only allows playback of the samples, with no specifi c control over the coding.