RECORDING VOCALS ON A COMPUTER
Recording Vocals On A Computer
Technique : Recording/Mixing
Recording to a computer can make it
easier than ever before to produce a great vocal sound — but there are
also pitfalls to watch out for...
Paul White
One of the most common questions we are asked here
at SOS is still "how can I achieve that 'produced' vocal sound?"
Now that so many of you are recording directly to computers rather than
to tape or dedicated digital multitracks, I thought it might be an idea
to explore vocal recording in the context of a typical computer-based
studio.
First Steps
The first issue with a computer system is how to
get a mic signal into it. Typical soundcards have only line inputs, or,
if they have mic inputs at all they're often designed for use with
consumer-quality microphones. Thus, you're always going to need either a
mixing console or a separate mic preamp to interface studio-quality mics.
If you're using a mixer, it is a good idea to
establish as short a signal path as possible. This entails using the
mixer's channel direct outs, if fitted, or even taking the signal feed
from the channel insert send. You can also feed signal out of the mixer
via an unused pre-fade aux send, which is an effective way of using a
simple 'something-into-two' stereo mixer for simultaneous monitoring and
recording. In general, the more unnecessary circuitry you bypass, the
cleaner the signal will be.
As regular readers will no doubt be aware, a
capacitor microphone will produce the best vocal results in the majority
of situations. To use one of these you'll need a mixer or preamp with
phantom-power capability, or possibly a separate phantom power supply
box. A few of the better audio interfaces with built-in mic preamps have
phantom powering, but if you plan to use one of these, make sure the
full 48 Volts is supplied, as many capacitor mics either fail to work
altogether or deliver a reduced level of performance on lower voltages.
Mic positioning for vocals is relatively simple.
The main things to remember are to keep the mic away from walls and
corners, and to hang up absorbent material against the walls if the room
sounds too 'live'. Always use a pop shield between the mic and the
singer, and work around nine inches from the mic. My vocal room doubles
as a store room, and it seems that the more rubbish I accumulate in
there, the better the acoustics get, presumably because the sound is
scattered rather than bouncing back from unobscured flat walls. Avoid
small square rooms with hard walls, as these can sound very boxy.
Pre-processing
When you work largely or exclusively on a
computer, signal processing tends to become something you do with
plug-ins, but it's actually useful to compress vocals with a
conventional outboard compressor at the analogue stage, before they
enter the soundcard's input and pass through its converters. This makes
the best use of the dynamic range of the converters. However, it's best
to leave room to add more compression later with your plug-ins, by
erring on the side of under-compression. To do this easily, set up the
amount of compression on the outboard unit that seems right for the
vocals, then adjust its compression threshold to produce around 3dB less
gain reduction than that 'ideal' setting.
Whether you record at 16-bit or 24-bit resolution is up to you, but my
experience has been that, for pop music vocals where the signal has been
compressed to some extent prior to being digitised, 16-bit is perfectly
satisfactory, even for serious projects.
Normally I advocate leaving EQ until mixing, but
there are some analogue equalisers that simply sound nicer than
plug-ins, so you may want to apply some EQ on the way in. I use an SPL
Channel One for all my computer recording, because it combines a clean
mic preamp with a nice compressor and a good-sounding equaliser, which
means that I can do all my processing in one place. Usually a little
high-end 'air' EQ combined with low-cut filtering, is all that's needed.
(If you do choose to use EQ on the way in, as with compression you
should take care not to overdo it.)
I recently fitted a digital output card to the
Channel One, which makes connecting to a computer very easy. If you're
using a budget soundcard with less-than-great converters, a preamp with
a digital output is a good way to get high-quality audio into the
system, provided that the soundcard has the appropriate digital input.
Setting Up To Record
Depending on your choice of audio interface or
soundcard, you may have enough separate outputs to enable you to set up
a foldback mix using the pre-fade sends on your sequencer's virtual
mixer. If you only have a stereo output, the singer will have to make do
with hearing what you hear in the control room. In practice, I tend to
send the singer the control-room mix anyway, as this can be rebalanced
to their taste without affecting my ability to record them. Having a
headphone amplifier within reach of the singer helps, though, as it's
useful for them to be able to adjust their own 'phones level.
Depending on the style of music you're producing, you may be able to get
away with recording vocals at the opposite side of the room to the
computer, to minimise fan noise, but ideally you'll want to put the
vocalist in a different room altogether — unless you have a very quiet
computer. The recording room needn't have a soundproof door, as you
don't need very much attenuation to cut out computer fan noise — and in
the absence of a talkback system, it's handy to be able to shout to the
singer without having to open the door! In my situation, it's often
enough to have the singer in the next room to the studio with the door
open, provided that they're slightly around the corner, to take them out
of the direct path of any computer noise passing through the door.
When recording in this way it's important to work
with the control-room monitors turned down fairly low, otherwise they'll
leak into the vocal mic. It's also a good idea to turn off any metronome
beeps, as these have a habit of leaking from the headphones into the
vocal mic.
Most singers perform better with a bit of vocal
reverb in the foldback, but not all software packages allow you to
monitor with plug-in effects. If you can, all well and good, but if not,
you might have to resort to using a hardware effects box. Those using
stereo-out soundcards have two alternatives: either add a little reverb
to the whole stereo mix during recording, or pan all the vocals to one
side of the soundcard output and all the backing track to the other,
then add reverb only to the vocal output. It's really a matter of
picking what the singer is happiest with, but when you don't have all
the facilities of a big hardware mixer to help, you have to improvise.
Of course, adding hardware effects to selected parts is not a problem if
you have a multi-output soundcard and an external mixer.
Make Do & Mend
Unless you're working with an impossibly good
singer, the need to redo or replace some parts of the vocal will
inevitably arise. Punching in and out on a computer system is certainly
possible, but many people prefer to create short 'patch-up' recordings
in a mode that doesn't overwrite the original audio. In most software
packages, if you record a part in a track that already contains audio,
you'll simply end up with a new section of audio sitting on top of the
old one, and whichever is on top will play. This system allows you to
easily decide whether the newly-recorded sections are satisfactory or
not. If you decide to keep them, you can then splice them into the main
vocal track. Bear in mind that if your system does not allow monitoring
of effects while recording there may be an unsettling change in the
sound at the punch-in point, as the original recording (with whatever
plug-in effects you've added) will be replaced by either a dry signal or
one to which hardware reverb has been added. Most singers can deal with
this, but you need to warn them first, or they'll think something has
gone wrong.
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Let's Go Round Again... Loop Recording Tips |
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One useful facility
offered by various MIDI + Audio sequencers is
'multiple-take' recording. In this mode, you set up a
loop of a section of a song, such as a verse or chorus,
initiate recording, and let the vocalist sing the
section over and over, as many times as they like, as
the sequencer automatically repeats the looped section.
Some software packages (including Cubase VST, in
which the process is called Cycled Recording, and
Logic Audio, in which it is called Loop Record)
place each subsequent take on its own track (its own
'lane' in Cubase), ready for you to audition the
takes and select the best bits of each for 'comping'
together. Others (such as Pro Tools LE, in which
the process is called Loop Recording) keep the takes on
one track but present a pop-up list of numbered takes
for auditioning.
Either way, the facility
allows the vocalist to really relax and get into the
swing of the section of vocal in question and the
engineer ends up with plenty of takes to choose from,
whether they're looking for just the best of the bunch
or good sections to paste together. Debbie Poyser |
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Mixing Vocals
Before getting too far into setting up a mix, I
find it useful to check the audio and trim out noises, such as coughs,
lyric-sheet page-turns, and so on, that occur during pauses in the
vocal. If you can still hear some computer fan noise on the vocals, as
you might if you had to record in the same room as the computer, you can
either manually silence the pauses, which is very tedious, or use a
'strip silence' type of function to chop the track up into sections by
removing silent pauses. This process works on a threshold system, rather
like a noise gate, but if you find it's taken out something that should
have still been there, you can usually extend the offending audio part
manually to get it back. That's the wonder of non-destructive editing —
it may have disappeared from the screen, but it hasn't really gone!
Alternatively, if the noise is fairly consistent and not too loud,
simply insert a gate plug-in and deal with it as you would when using
hardware. As a rule, gating should come before compression, as that will
make it easier to set the gate threshold, and always before reverb or
delay plug-ins, to avoid cutting off reverb or delay tails. Indeed,
reverb can help disguise an edit or gate action that might not stand
scrutiny in isolation.
Though you may have compressed your vocals during
recording, you may still need to add a little more compression using a
plug-in. If this isn't enough to tame all the vocal highs and lows, you
can always use the sequencer's mix automation to nudge the vocal-channel
level up or down as appropriate. Furthermore, because VST II plug-ins
can be automated, you may find that just increasing the compression
ratio in difficult-to-tame sections does the trick.
The best reverb plug-in for vocals won't necessarily be the most
processor-hungry one you have. Often a less dense reverb will sound more
flattering, supporting the sound without clouding it too much. Adding
some pre-delay (between 50 and 100mS) will produce a subtle doubling
effect that helps beef up weaker voices.
Whatever you think of the ubiquitous Auto-Tune
plug-in, it's true to say that even good singers can benefit from a bit
of subtle Auto-Tune assistance. For singers who are already
reasonably precise, I find that slowing the response speed a little from
the factory default setting works best and provides the best trade-off
between pitch correction and unwanted side-effects. Set the appropriate
scale for the song, rather than relying on chromatic mode, especially if
the singer uses strong vibrato — it can translate into unwanted semitone
trills!
If there's a key change in the song, I've found
the easiest way to handle it is to create a new vocal track for the
key-changed part, move the relevant audio into it, then open a new
instance of Auto-Tune, set to the new key. Occasionally you'll
find a phrase that doesn't respond well to Auto-Tune, either
because it uses very dramatic pitch slides or because it includes notes
not in the main scale. Again, this is easily dealt with by creating yet
another vocal and moving the 'phrases to be left alone' into it. You
don't have to duplicate all your plug-ins for each track, as the reverb
can be set up on a post-fade send, and if you use a lot of insert-type
effects or processes you can route the channels via a buss/group, and
then put the plug-ins in the buss or group insert point.
Auto-Tune is also useful for creating
instant double-tracking effects. Simply run a copy vocal track that
hasn't been processed with Auto-Tune alongside one that has.
Introducing a small delay offset between the two and panning them to
different sides helps the illusion. Using a short, tempo-related delay
on one or both tracks also produces a nice doubling effect, but unless
applied very subtly it can be rather obvious, so make sure it suits the
song.
A more natural way of doubling choruses is to copy
a chorus from one part of the song and layer it with a chorus elsewhere
in the song. The original performance will be slightly different each
time the chorus is performed, so layering sounds in this way is bound to
sound more natural. Avoid using Auto-Tune, if possible, when
you're doing this, or use it only on one part. Otherwise you'll tune out
the small natural differences that create the double-tracked effect.
It's also best to save double-tracking for parts of the song that need
beefing up, as it can lose its impact if used all the way through a
song.
Vital Voices
As you can see, creating a high-quality, produced
sound doesn't necessarily mean using an expensive studio. And there are
lots of other tricks you can try in addition to the ones already
mentioned. For example, use a tube emulation plug-in to get more of a
valve-mic sound, or process a vocal part through a slow rotary speaker
effect for that trippy, John Lennon sound. The main thing is to take
care to get a good clean sound at source and to get that sound into your
computer without degrading it. Process only as much as you have to, and
use effects for a reason, not just because you happen to have the
plug-ins. Where you have several plug-ins that do the same job, such as
compressors and reverbs, take the time to try them all and see which
works best. You may find that the best sound comes from the least
expensive plug-ins, so always go by your ears, not by the price tag. |
