Audio: sampling (0:06)
sampling plays the sound of a creaking door, followed by the sound of wind chimes. Both sounds are samples taken from a sample library. The sampling figure shows the composite waveform.
Sampling is the process of obtaining a prerecorded sound. A sample library is a collection of prerecorded sounds.
The traditional view of sampling treats it as a process of obtaining a short excerpt of music from a longer piece of music that has been written and recorded by someone else. This is a narrow definition of sampling. It is also why sampling is a contentious issue. Obtaining a sample from someone else and using it without their permission may infringe copyright.
The guide uses a wider and simpler definition of sampling. A sample is simply a prerecorded sound. Typically, it is a sound with a short duration although what constitutes short duration is deliberately left vague. The sample may contain pitched sound or it may contain unpitched sound or it may be a mixture of the two.
There are three safe and legal ways to obtain a sample. One is to record yourself with a microphone. Another is to use synthesis to generate a digital sample. The third is to obtain a sample that is in the public domain.
A digital sample is recorded at a specific sample rate. A sample recorded at a specific sample rate plays back correctly at that rate. It will not play back correctly at another rate, its pitch and duration will change. Resampling is the process of converting the sample rate. Every music programme and app should allow you to manually set the correct sample rate for playback and some will automatically resample behind the scenes.
Three common sample rates are:
- 44,100Hz for a CD. It is currently the most widely used sample rate.
- 48,000Hz for Digital Audio Tape (DAT). It is High Definition (HD) audio.
- 44,100-192,000Hz for DVD.
Once a sample has been obtained, it can be used immediately to write music, or processed further into a sound effect, or stored in a sample library for future use.
A sample library is an excellent resource for a music writer. Recorded samples made with a microphone can be combined with computer-generated synthetic samples to build a library of reusable sounds and instruments. The library can be extended further by downloading samples in the public domain from the internet or purchasing a sample library from a commercial provider. The popular Freesound website provides samples with Creative Commons licences governing their use.
MIDI provides a ready-made virtual orchestra for writing music. MIDI instruments are included in nearly every computer music programme and app. General MIDI Level 1 (GM1) includes 128 musical instruments and 47 percussion instruments. General MIDI Level 2 (GM2), also known as Roland GS, extends the size of the orchestra to 256 musical instruments and 62 percussion instruments. A sampler is a computer instrument containing prerecorded samples and based on MIDI. Many more instrument samples are available as plugins, software that adds extra functionality to an existing programme.
A soundfont is a sample library for playing a MIDI instrument. It is old technology, meaning it is a little more complex to set up and use than a modern sample library. However, there are many soundfonts available on the internet, and all of them can change the timbre of an instrument significantly. Soundfonts are used to produce most of the music in the guide.
Incorporating a sample in your work may be subject to copyright. A sample is a sound recording and a sample library, including a soundfont, is a collection of sound recordings. It may seem a little strange to think that someone can copyright, and possibly make money from, the sound of a guitar string, yet that might be the case. It is always advisable to check with the author of a sample what permissions are granted for their use and whether they extend to performance and recording, including on a website or in a digital ebook.