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3.
The Sound Source
There are only two ways to get your sonic information onto the tape, through
a microphone or directly from an electronic output. In general, the quality
of what comes back is affected by the quality of the equipment the signal
passes through.
a. Voices, Horns and Acoustic Piano
While the human voice is the most dynamic, all of these instruments present
a similar problem to the engineer. How can we preserve the performance, that
is the soft and loud of it, and get it accurately on tape? With these instruments,
we usually have to use a microphone.
The two main types of microphones are "dynamic", which have no active electronics
involved in amplifying the input signal, and "condenser", which require either
batteries or "phantom power" to power their electronics. Both types have a
thin membrane, called the diaphragm, that vibrates and that physical vibration
is translated into an electronic signal. In general, condenser mikes are brighter
and have a broader frequency response, but they are more fragile. That's why
you usually see an SM57, a general purpose dynamic mike, in the lead singer's
hands at a concert. They can withstand a lot of abuse.
Classic condenser microphones like the Neumann U-47 and AKG C-12 use vacuum
tube electronics and are treasured for their unique sound. They are rather
large and have diaphragms 2 inches in diameter. Ribbon microphones are another
vintage design that incorporates a thin rectangular strip as it's diaphragm,
hence the name. PZM designs are a relatively new invention. They work on a
completely different principle and don't look anything like traditional microphones.
The signal created by the microphone is very small and it is the microphone
pre-amp that increases this level to what is known as "line-level" for interfacing
with the mixing board. This is yet another link in the chain with it's opportunity
to affect the sound, and they do.
Everyone has their favorite microphones and pre-amps for different situations
and most do color the sound. The important thing is whether you like that
color and if it's appropriate for the particular situation at hand. Here again,
we run into the concept of "flat frequency response" and again it is relatively
meaningless. Most microphones are not "flat" and some are better suited for
certain jobs than others. As always, you need a reference and in this regard,
frequency response charts and the like can be useful. Rules are made to be
broken.
Signal processing is another powerful weapon for your sonic arsenal. The
judicious use of compression can be a big help in lots of situations. Compressors
were originally developed to compensate for the limited dynamic range of analog
tape. Basically, they make the soft parts a little louder and the loud parts
a little softer. This performs the dual function of keeping the soft passages
higher above the "noise floor" and preventing the loud parts from getting
too loud and peaking into distortion. Most compressors allow you to change
the "range" (1:1, 2:1, 4:1, etc.) and the "attack time" and "release time"
of the effect.
Expanders and Limiters are related to compressors. Expanders make the soft
parts softer and the loud parts louder. Like compressors, you can set the
range, and attack and release times of the effect. With limiters you can set
a threshold that cannot be exceeded. Noise Gates simply do what their name
implies by shutting off the signal path when there is no input.
b. Guitars, Basses and Things With Strings
String instruments can be recorded acoustically with microphones or directly
if they have pickups. There is a different sound to each and in different
situations, one may be more appropriate than the other. Often, both are recorded
simultaneously and blended together in the mix. Electric guitars and basses
are recorded through microphones on the amplifiers and direct to be blended
or used seperately later in the mix. All the just mentioned signal processing
definitely applies here, too.
The Rockman headphone guitar amp, invented by Tom Scholz in the mid 1980's,
started the revolution in small, electronic amp simulators. Rackmount guitar
pre-amps have gotten very sophisticated in the last few years, offering tube
pre-amp stages, multi-effects, MIDI and memory capabilities. There's still
nothing quite like a Gibson Les Paul into a 100 watt Marshall stack, but that
can get dificult for the neighbors!
c. Samplers, Synthesizers and Drum Machines
All of these devices have direct outputs and can be connected straight
to your mixer. A lot of them also include built-in effects and it's up to
you whether you want to print them "wet" or "dry". It will probably depend
on how many tracks you've got to play with, but you can print sounds and their
effects seperately. This way if you change your mind about that "big reverb",
you're not locked in.
Playing one sound at a time to tape has never been a problem but these
days, there's a lot of sequencing going on and most of these boxes only have
2 or 4 outputs. In 4 or 8-track recording, this is an asset and you just have
to mix the sounds from inside the box. In a professional 24 or 48-track situation,
you'll want individual sounds on individual tracks. Two ways to do this are
mute the sequencer tracks and record each sound in successive passes or turn
down the internal volumes of all the sounds and turn one on at a time as you
make passes.
Drum machines are a powerful tool and have become a mainstay of modern
music making. They all have unique sounds and many have become associated
with specific types of music i.e. the Roland 808 and EMu SP-12 with rap and
the Roland 909 with dance. Some also have sampling capabilities and built-in
audio triggering for replacing sounds off tape. Earlier models were designed
with pads for programming, and some people still prefer that. Now most are
available as sound modules like any other synth and the programming is simply
done from the keyboard and sequencer.
Samplers are basically digital recorders. The earliest models could only
record and playback one sound at a time. In the early 80's, many a snare was
replaced by hand with a steady index finger and the AMS sampler. Two of the
earliest MIDI samplers were the Akai S-612 and Ensoniq Mirage. They were 8-bit,
which refers to their sampling resolution. Technically, the higher the resolution,
the more accurate the sample. Again, specs are one thing and sound is another.
These boxes all sound different and they do what they do, differently. If
you like the sound of your old 12-bit box, then go for it.
Polyphonic samplers began to appear in the mid 80's, among them the Casio
FZ-1 and Akai S-900, S-950 and stereo S-1000 units. Resolution evolved to 12-bit and then 16-bit and MIDI
made these boxes even more powerful. In the studio, samplers are great for
quick repairs, flying vocals around or moving tracks. A sequencer and a sampler
locked to tape in the mix can be real handy for those last minute repairs
and arrangement changes.
d. Real Drums and Real Drummers
There are two things that you need to get good live drum sounds, a properly
tuned, great sounding kit and a properly tuned, great drummer. If you can
only get one, go with the human. You can always replace the sounds.
The basic approach to drum miking involves a separate mike for the kick,
the snare, the hat, the toms and one or two overheads to get the cymbals and
the room sound if there is one. Another snare option is to put one mike underneath
and one on top. Some of the great drum sounds from classic rock records were
recorded with two mikes on the whole kit! The miking techniques should reflect
what kind of drum sound you're going for.
Compression can be a big help when recording drums because of the transient
nature of the instruments. Depending on the parts being played, use it as
needed. Sometimes gates can be helpful as well, especially when the rhythm
section is being recorded in the same room. Noise gates with "sidechain" capability
allow you to select what frequencies will open the gate. Another excellent
device for this application is the "Kepex" expander/gate whose operation is
frequency dependent.
Many engineers like to slam high levels on to analog tape to get the natural
"tape compression" sound. Some even go to the lengths of recording drums on
2" 16-track analog and then transferring that to another format to complete
the project. Hey, if you've got the budget and the time, go for it.
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