2. Week 5
Sampling
…the most ubiquitous synth engine
• What is a Sampler?
• How does it differ from a subtractive
synthesizer?
• Special Sampling Terms
3. reminder… BASIC SYNTHESIS
Source
MIDI
- Pitch of Note
- Velocity of Note
- Duration
Modifiers
Signal Processors
Audio
Function Generators
4. 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…?
5. Note Pitches, Tone Color and Shape
Source Osc Frequency
MIDI
Pitch of Note eg: C3
Frequency Multiplier
MIDI
Pitch 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.
6. 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…
7. How to extend the wave and deal with
different pitches?
Source Osc Frequency
MIDI
Pitch of Note eg: C3
Frequency Multiplier
MIDI
Pitch of Note eg: C4 Audio
8. The sound of real instruments…
Source Source Source
MEMORY MEMORY MEMORY
Does a piano, for example, just make one unique sound…?
9. 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 secs
That’s nearly two and a half hours of recorded samples…!!
10. Back to the real world…
Can sampling be more efficient…?
1. Do we need to have a sample for every key? Not necessarily
2. Do we need a separate sample for every dynamic layer? No
3. 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 looping
2. Using samples over limited keyboard ranges (multi-sampling)
3. Using filters to replicate the effect of dynamics
12. Sampling - looping
First, we have to find a small portion of the wave that will loop
smoothly. With musical instrument sounds this can usually be
found after the initial transient has passed and the sounds decay
settles down
13. Sampling - looping
The sampling “engine” can now continuously repeat the section of
the wave selected for looping. Tools such as crossfading can make
the looping smooth. We now have a wave that will sustain
forever…
14. Sampling - looping
The final step is to apply an amplitude envelope – just as we do
with the standard synthesizers.
15. Sampling - multisampling
Why do we need different samples for different pitches? Can’t the sampling
engine multiply the frequency to get the pitch of any note, like the basic
synthesizer…?
With the basic wavetable synthesizer, the oscillator was producing a very
simple wave which has the same timbral characteristics at all pitches. Real
instruments essentially make different sounds at different pitches, so simply
multiplying the frequencies in the sampling engine to get different notes
from one instrument sample, simply doesn’t work very well.
A look at the spectrum will help explain why, then let’s listen to an
example…
17. Sampler “pitch engine”
Real Piano Note Real Piano Note
B3 B5
Sampler Note Sampler Note
B3 ( B5 / 4) B5 ( B3 x 4)
18. Sampling – multi-sampling
Sample-1 Sample-2 Sample-3 Sample-4 Sample-5
Multi sampling is about using a single sample across just a limited
number of keys – usually called a zone – where the effects due to
the sampling pitch change are acceptable
19. Sampling – Filter for dynamics
We saw with basic synthesis that the filter can be used to make a sound
brighter or more mellow by subtracting overtones or harmonics from the
original sound.
By linking the filter cutoff frequency and the overall amplitude, to the
velocity (dynamic) of the note, we can simulate the effects of loud and soft
playing.
filter open
Play Loud
filter closed
Play Soft
20. 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-5v2
play Sample-1v1 Sample-2v1 Sample-3v1 Sample-4v1 Sample-5v1
harder
21. Drum Machines & Groove Loops
Others applications of sampling.
Originally, sampling was seen as a synthesis method that enabled the
realistic synthesis of acoustic instruments and sounds, and it remains the
most common method of synthesis today for these purposes.
However, musicians and engineers soon realized that multi-sampling does
not need to be restricted to the sounds of one instrument, like a piano.
For example - drum machines work on the basis of putting a separate
drum 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 as
well for longer rhythmic wave files as with the small sustained portion of
acoustic instrument sounds. And so groove looping was born...
22. Sound Libraries
Special case of sampler content.
Sampler sound libraries are slightly different to synthesizer patches
because they contain two distinct types of files
1.The parameters and settings of the sampling/synthesis engine –
equivalent to the patches and programs associated with subtractive of
other types of synthesizers
2.The instrument source files - samples and multi-samples
whereas a synthesizer patch might contain instructions like “Set the
controls 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”
23. Summary
Samplers are Synthesizers. They use a wide variety of digital audio as the
wave 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
