Sampling
Sampling is “using a pre-recorded audio as the stems for new musical ideas.”
A sample can be anything from a second-long section of audio from a found sound to an 8-bar section of audio from another person’s song/recording.
Specification 👇
Component 2 Specification
Component 3 Specification
Component 4 Specification
Editing Samples
Cutting/Trimming
Cutting and trimming is what it sounds like it is – cutting your sample to the size that you want. For example, you might want to include just a little bit of the audio clip that you have sampled, so you cut out the part that you want and use that.
When cutting, however, it is important to take zero-crossing points into consideration. A zero-crossing is “the point at which a waveform has a value of zero displacement. Used as the point to edit audio to avoid unpleasant audible clicks.” As the definition states, it’s important to cut on a zero-crossing point to avoid clicks where a waveform may otherwise have been stopped abruptly.
Tuning
Tuning your sample means making sure that it matches the key that your composition is in.
Looping
A loop is “an audio or MIDI file of any length that repeats multiple times.” A loop point is the point at which one loop ends and another begins. Again, it is important to have the start and end of your loops on zero-crossing points.
You can crossfade a loop. A crossfade is when the last part of the audio file fades out as the next loop starts to fade in.
Samplers, Pitch mapping and Velocity Layering
A sampler is an instrument, hardware or software, that plays back samples. These samples can be musical or non-musical sounds, for example it could be a sample of a musical instrument, a sample from a song or a found sound or sound effect. Some samplers have sounds already loaded on to them by the manufacturer but others allow the user to add their own samples.
When working with musical samples, pitch mapping is used. This process involves matching the pitch of the sample to the corresponding key on a keyboard. For example, a sample with the pitch of a middle C will be mapped to the middle C key on the sampler.
If you were sampling a specific instrument, you might record the full range of notes that the instrument can make so that each file/note can be pitch mapped to the sampler's keyboard. However, because of pitch shifting technology that changes the pitch of a sound without affecting the length, you no longer have to sample every single pitch that an instrument can make, just every few notes. This is known as multisampling.
In other words you can shift the pitch of the sample to match surrounding keys on the keyboard. For example, if your middle C sample was stretched up to an E, when you played either the C, C#, D, D# or E key, the original middle C sample would be played but pitch shifted to the relevant pitch (D would sound like a D, E would sound like an E etc).
An obvious advantage of multisampling and pitch shifting is that it saves you time and file storage space as you don't have to record so many samples. However, pitch shifting technology only works so well until digital artifacts start to be introduced to the sound. A digital artifact is any unwanted sound that is added as a result of digital processing. A good rule of thumb for avoiding this is sampling every five notes so that samples only have to be stretched up or down five keys (eg C to F).
When you import a sample into a sampler, the default is for that sample to be played whatever velocity the key is played at. In other words, no matter if the user plays the key softly or hard, the same sample will be triggered.
Velocity layering is "the process of triggering a different sample for different note velocities to represent the timbral change when, for example, a key is played harder on a piano."
A sampler will sound far more realistic if you have a sample of the instrument playing each note a different velocities. Then you can program your sampler to trigger a different sound file based on the velocity at which the key is played.
Advanced Sampling Parameters
Reversing Samples and Stuttering
Reversing samples is pretty self explanatory; it means “playing a piece of audio backwards.”
Stuttering is “when audio is triggered repeatedly and quickly to make the audio sound like a stutter."
Applying synthesis parameters to your sample could include manipulating the ADSR envelope of the sample, setting a cut-off frequency or applying a high pass or low pass filter. For more information on this stuff, please click here.
Pitch and Key Zones
Setting the pitch zone means setting the pitch of a sample in your sampler.
Setting the key zone means setting the key in your sampler so that your samples can be tuned accordingly.
Velocity Layering
Velocity layering is "the process of triggering a different sample for different note velocities to represent the timbral change when, for example, a key is played harder on a piano."
Time Stretching
Time stretching is the process of changing the speed of the duration of a sample or piece of audio without changing the pitch. Normally, when you change the duration of a note, the pitch of the note changes because the wavelength changes, but time stretching uses some clever maths to stop this from happening (you don’t need to know how this works for your exam, but if you’re interested, this article is pretty good at explaining it all).
Sample Rate and Bit Depth
This is a brief overview of sample rate, bit depth, analogue and digital signals. This page has lots more information on the subject.
To convert an analogue audio signal to a digital audio signal, an A/D converter is needed. An A/D converter works with sample rate and bit depth to do this.
Sample rate is "the frequency with which a sample of analogue information is taken for conversion into a digital signal. Measured in Hz."
Bit depth, not to be confused with bit rate, is “the number of bits used in each sample in analogue to digital conversion.”
Sample rate controls the frequency resolution of the digital signa and bit depth controls the amplitude resolution.