Use of a hard drive in audio recording Hard disk drives play an important role in the process of audio recording. Depending on preference, factors such as memory storage, ability to stream from music sample libraries and the speed at which files or documents can be opened or saved – the read and write speed of the hard drive – are important to audio recording. As is the case with any usage of a hard disk, a greater read and write speed means a better performance. The speed at which music files can be opened and saved and transferred can be impacted greatly depending on the reading and writing speed of your hard disk drive. If you were to load a large amount of audio data on to your hard disk, a speed of 100 mb/s (megabytes per second) could equate to a long period of waiting and saving anything could mean more waiting. A more expensive hard disk drive could achieve speeds closer to 400 mb/s for reading and writing, theoretically resulting in a quarter the waiting time. Data Transmission Audio Interfaces – which are used to connect an instrument to a digital audio workstation – connect to a computer and communicate with the computer with a program known as a data transfer protocol. One of these is USB and due to its common usage, most computers have a USB port for connecting a USB device. Other devices use different protocols, such as Firewire, which is less common and computers are slightly less likely to have a port for connecting a Firewire device. Different protocols have different data transfer speeds. A greater transfer speed means more instruments can be recorded at once, so for certain ensembles a high data transfer speed could be considered necessary. USB 1.0 had a slow data transfer speed of 12Mbps (bits per second), which creates difficulty for anyone using this protocol. The more recent USB 2.0 has a much higher transfer speed of 480Mbps, enabling more inputs. Thunderbolt is a protocol with incredible transfer speed, 10Gbps. This allows for an almost endless number of instruments to be recorded at once. Signals An audio signal is the waveform produced by an instrument and recorded onto an audio track on a computer. A MIDI signal however is a representation of keys being pressed on a MIDI keyboard. It has no sound until sound is allocated to the MIDI signal and is recorded on a MIDI track. MIDI data types include absolute and relative. Absolute MIDI data is simply a configuration in which MIDI directly corresponds to the set controls, meaning if a MIDI controller sets the volume fader to a certain level, the MIDI data on the computer will be configured the same way. Relative data modes do not directly correspond to set controls; they correspond to the software settings rather than hardware controls. MIDI keyboards tend to have the ability to detect velocity. The force with which a key is pressed allocates a velocity value to the created note. This value is often used to give the note more volume, simulating exactly what a piano key would do if pressed with force. An audio file has a dynamic range – the range of largest to smallest signals that it can record. This is determined by the bit depth (the number of bits per sample). The greater the bit depth, the greater the range of volumes that can be recorded. Certain sounds can be “clipped” unless an appropriate bit depth is used when recording. Nyquist’s theorem illustrates the frequency range of an audio file, which is determined by its sample rate – a measure of the frequency of audio sample carried in a second (Hz). In order to produce the range of frequencies an audio file contains, Nyquist’s theorem states that the sample rate must be more than twice the maximum frequency of an audio file for the audio to be correctly represented in digital form. 44100 Hz is a common sample rate as it covers the full range of frequencies a human can hear. Peripherals Several peripherals – devices which may be connected to a computer are pertinent to music sequencing and programming. An audio interface is a device which connects a musical instrument or piece of equipment to a computer enabling it to be recorded directly into a digital audio workstation. MIDI recording requires a MIDI interface of some description to provide MIDI data. This is commonly manifested as a MIDI keyboard which could be plugged directly into a computer and MIDI signals produced could go straight to a digital audio workstation. Many audio interfaces also have an input for a MIDI device and an output to then connect to a digital audio workstation. Many MIDI devices with inputs and outputs can be connected together into a chain and then connected to a digital audio workstation. The relationship between the computer and its peripherals is managed by the computer’s operating system which communicates with peripherals with software known as a driver. Each peripheral has its own driver and requires this driver to be downloaded onto a computer for the computer to utilise the peripheral. Drivers are necessary for the operation of peripherals. Sequencers A sequencer is a device such as a computer program or electronic instrument that utilises and orders data to produce music. It enables one to create and edit tracks for MIDI or audio. With the use of an audio interface, audio can generally be recorded onto a sequencer. It can then be edited, mixed and played back as a user of the sequencer so desires. A sequencer will generally have the ability to record, edit and playback MIDI from a device connected to the sequencer. MIDI may be edited or created on a sequencer itself rather than played from an external MIDI instrument. Whether audio or MIDI is recorded, both formats can be mixed and often can have effects added to them such as compression. Sequencers also generally have the ability to edit and play sampled audio from a different recording or piece. A computer program designed for the process of sampling is generally used to siphon audio from a source and insert the audio into a sequencer where it can be edited and played back in the same fashion as a recorded audio or MIDI track.