The following are some of the common formats:
AIF (Audio Interchange Format). This is a computer file format. AIF is most commonly found on Macintosh computers, but many Windows programs can also read these files. These sound files can be "mono," "split stereo," or "stereo interleaved" files. Split stereo files contain two separate-but-linked files whose file name ends in "L" and "R." Interleaved files show up as one stereo file. While many dedicated sound editing programs can read all three types of AIF files, most of the popular multi-track hard disk audio software and hardware out there only reads mono and split stereo files, but will import interleaved stereo files. This format can embed "loop points" in the file. This file is capable of most sample rates and bit depths.
SDII (Sound Designer II Format) This file format, pioneered by Digidesign, is similar to AIF. Stereo files in this format are commonly "split stereo" (two mono sound files that make up one stereo file), but may also be interleaved. These files must be interleaved before they can be burned to an audio CD. This is the native format of MotU's Digital Performer, and Digidesign's ProTools hard disk recording programs (ProTools HD 192 now uses the WAV format).
WAV (Microsoft Windows Audio Format) This is a computer file format that was first associated with Windows PCs. Although still most common on PCs, Macs are also able to read this format. It can contain marker information, but not loop points. This file is capable of all sample rates and bit depths and can also be mono or stereo files.
MP3 A highly compressed audio format commonly used in Web and multimedia presentations, as well as portable audio players. Its files are about one-tenth the size of AIF and WAV files of the same length.
RX2 The format used in the Recycle software from Propellerhead. A unique format that contains imbedded "slice" information that allows you to stretch and compress a file without changing the pitch. It also contains MIDI information about where the timing of the slices falls, that certain software programs can import, thus making changing the feel of the loop much easier.
Sample rate is the number of times per second a sound has a snapshot taken of its waveform. CD quality is 44.1K, or 44,100 snapshots per second. Half the sample rate is roughly the highest frequency that that sample rate can represent. The 44.1K sample rate was chosen because it can represent frequencies of up to around 22K, which covers the complete human audible hearing range (for most of us anyway).
Common Sample Rates: 22.05K: Multimedia & Web presentations 44.1K: Audio CDs 48K: Video production 96K: DVDs
Bit Depth This is the number of binary 0s and 1s used to describe each snapshot. The more bits, the more accurately the sound is reproduced. Although audio CDs use 16bits, 24bit is now the common recording standard – it just plain sounds better. The higher the number of bits used, the wider the dynamic range of the sound.
Back when I first started creating loops (hand me my arthritis medications please), the music technology available for creating and editing loops made the process somewhat complex and time consuming. Back then, there were no CD-quality hard disk recorders, and practically no sound editing software. Personal computing power was limited and expensive. Loops were created and sampled into stand-alone samplers. Editing was done by numbers that represented samples per second, or by ear (muffled gasp). All this has changed in the last decade. We now have inexpensive, high-quality gear that makes the recording and looping process much easier.
My looping setup is pretty simple. Depending on the client, I'll either use a Roland VS-2480 standalone hard disk recorder (a complete studio in a box), or a Macintosh G4 with a Mark Of The Unicorn 828 firewire audio interface. Both setups are similar in cost.
The VS-2480 is truly a studio in a box. It has built-in microphone preamps, expandable effects, and motorized faders. Put sound in, and out pops a finished audio CD. When you plug a video monitor, keyboard, and mouse into the 2480, the lines between a computer and standalone hard disk recorder are blurred. It's the only choice if you're computer-phobic. Plus, I've never seen a VS recorder crash – wish I could say that for computers.
Now, I've been a computer geek forever. My first computer was an Apple Macintosh I bought in March of 1984, and I have owned countless Macs since then. The new 800Mhz iMac G4 and the MotU 828 are the basis of my computer hard disk recording system these days. The iMac is compact, fast, and has a LCD flat panel display that is easy on the eyes, which is very important when you spend lots of time in front of the screen. There are good PC-based recording systems out there, but I admit that I'm biased.
To deliver the loops to your client, you'll need to have a CD-R drive (to burn a CD of your work). Most new computers come standard with at least a CD-R drive. My new Mac will even burn DVDs!
You'll also need some sort of speakers to monitor your audio. Don't use stereo speakers! There are lots of great inexpensive studio monitors available, both powered and un-powered. With studio monitors you'll more accurately hear what's truly going on with the sound.
The previous two examples of hardware are at the top end of the home/production studio scale. There are also some much less expensive pieces of gear that are available to get your feet wet in looping. Although I won't discuss these in depth, check out the Roland SP-303 Phrase Sampler, and the brand new Roland MC-09 Phrase Lab. The Phrase Lab has many of the same capabilities as the software that will be discussed in the next section. They both use inexpensive Smart Media memory cards to store and transfer files between units and computers. Both these pieces are an inexpensive, great sounding way to get into looping.
Although standalone recorders all use software, which in most cases can be updated, it is relatively transparent to the user. This is not so with computers. The world of music software for computers has exploded in the last few years, and offers many things that were once available only through hardware.