Week 5Sampling …the most ubiquitous synth engine • What is a Sampler? • How does it differ from a subtractive synthesizer? • Special Sampling Terms
reminder… BASIC SYNTHESIS Source MIDI- Pitch of Note- Velocity of Note- Duration Modifiers Signal Processors Audio Function Generators
SAMPLING Source MIDI MEMORY- Pitch of Note- Velocity of Note- Duration Modifiers Signal Processors Audio Function Generators Can we just replace the source with an instrument recording…?
Note Pitches, Tone Color and Shape Source Osc Frequency MIDIPitch of Note eg: C3 Frequency Multiplier MIDIPitch of Note eg: C4 Audio But remember, the oscillators are buzzing away continuously – envelope generators shape the individual notes, and filters control aspects of tone color.
SAMPLING Source MIDI MEMORY- Pitch of Note- Velocity of Note- Duration Modifiers Signal Processors Audio Function Generators The basic principle of sampling seems straightforward, but there are questions…
How to extend the wave and deal with different pitches? Source Osc Frequency MIDIPitch of Note eg: C3 Frequency Multiplier MIDIPitch of Note eg: C4 Audio
The sound of real instruments…Source Source Source MEMORY MEMORY MEMORY Does a piano, for example, just make one unique sound…?
The “PERFECT PIANO SAMPLER” For the “Perfect Ultimate Piano Sampler”…1. We’ll need a recorded sample of each of the piano’s 88 keys, (BTW: a piano’s low key can lasts 50 seconds when struck and sustained, a high key about 5 seconds so the average length would be about 25 seconds).2. Let’s say an average pianist wants to hear 4 levels of dynamics – soft, low-mid, hi-mid and loud. That makes it 4 samples per key.Total number of seconds of recording…88 x 25 x 4 = 8,800 secsThat’s nearly two and a half hours of recorded samples…!!
Back to the real world… Can sampling be more efficient…?1. Do we need to have a sample for every key? Not necessarily2. Do we need a separate sample for every dynamic layer? No3. Do we need to record the whole natural length of a note? No So, yes it can be more efficient by…1. Extending shorter sample recordings by looping2. Using samples over limited keyboard ranges (multi-sampling)3. Using filters to replicate the effect of dynamics
Sampling - loopingStart with our original wave – for example a long piano note
Sampling - loopingFirst, we have to find a small portion of the wave that will loopsmoothly. With musical instrument sounds this can usually befound after the initial transient has passed and the sounds decaysettles down
Sampling - loopingThe sampling “engine” can now continuously repeat the section ofthe wave selected for looping. Tools such as crossfading can makethe looping smooth. We now have a wave that will sustainforever…
Sampling - loopingThe final step is to apply an amplitude envelope – just as we dowith the standard synthesizers.
Sampling - multisamplingWhy do we need different samples for different pitches? Can’t the samplingengine multiply the frequency to get the pitch of any note, like the basicsynthesizer…?With the basic wavetable synthesizer, the oscillator was producing a verysimple wave which has the same timbral characteristics at all pitches. Realinstruments essentially make different sounds at different pitches, so simplymultiplying the frequencies in the sampling engine to get different notesfrom one instrument sample, simply doesn’t work very well.A look at the spectrum will help explain why, then let’s listen to anexample…
Sampler “pitch engine”Real Piano Note Real Piano Note B3 B5 Sampler Note Sampler Note B3 ( B5 / 4) B5 ( B3 x 4)
Sampling – multi-samplingSample-1 Sample-2 Sample-3 Sample-4 Sample-5Multi sampling is about using a single sample across just a limitednumber of keys – usually called a zone – where the effects due tothe sampling pitch change are acceptable
Sampling – Filter for dynamicsWe saw with basic synthesis that the filter can be used to make a soundbrighter or more mellow by subtracting overtones or harmonics from theoriginal sound.By linking the filter cutoff frequency and the overall amplitude, to thevelocity (dynamic) of the note, we can simulate the effects of loud and softplaying. filter open Play Loud filter closed Play Soft
Sampling – velocity layers for dynamics A more sophisticated (and true to the principles of sampling) method of introducing dynamic timbral behavior based on effort or force, is to use “velocity layers”… Sample-1v3 Sample-2v3 Sample-3v3 Sample-4v3 Sample-5v3 Sample-1v2 Sample-2v2 Sample-3v2 Sample-4v2 Sample-5v2play Sample-1v1 Sample-2v1 Sample-3v1 Sample-4v1 Sample-5v1harder
Drum Machines & Groove Loops Others applications of sampling.Originally, sampling was seen as a synthesis method that enabled therealistic synthesis of acoustic instruments and sounds, and it remains themost common method of synthesis today for these purposes.However, musicians and engineers soon realized that multi-sampling doesnot need to be restricted to the sounds of one instrument, like a piano.For example - drum machines work on the basis of putting a separatedrum sound (snares, toms, cymbals, blocks and so on) on different keys,allowing a “multi instrument” to be played at one time from a keyboard.In addition, playing back wave loops with a synthesis engine works just aswell for longer rhythmic wave files as with the small sustained portion ofacoustic instrument sounds. And so groove looping was born...
Sound Libraries Special case of sampler content.Sampler sound libraries are slightly different to synthesizer patchesbecause they contain two distinct types of files1.The parameters and settings of the sampling/synthesis engine –equivalent to the patches and programs associated with subtractive ofother types of synthesizers2.The instrument source files - samples and multi-sampleswhereas a synthesizer patch might contain instructions like “Set thecontrols like this and set the oscillator source to a sawtooth wave”a sampler patch might say “Set the controls like this and use those samples,stored in that folder, as the source wave for each keyboard zone”
SummarySamplers are Synthesizers. They use a wide variety of digital audio as thewave source. It is important to understand these facts about samplers… 1. Samplers use a source wave file, called a “sample” as the basis of a sound. This sound (if musical) will have an original key. 2. For realism, it is necessary to sample instruments at different pitches and make multi-samples with different samples attached to different zones of the keyboard (or pitch range of the instrument) 3. Samplers can make use of filters and other synthesizer controls, just like subtractive synthesizers 4. Voice libraries for samplers include the program parameters and the sample files