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Simulating Analog Tape
Flange In SONAR

Studio Overviews

Posted by CapnZilog - Jun 08, 2006
@ 07:51:55 PM

mp3

Old-skool your mixes with a
dramatic 70's technique

The Digital Simulated Analog Tape Flange
Effect

Guitar School

6/8/06

Back in the days of Elvis and the early Beatles, where
4-track reel to reel
recording was considered
state-of-the-art, tape machines were more than
just
recording devices; they were also used as
effects. And one of the
earliest effects was
Automatic Double Tracking, which is synonymous
with
rockabilly vocal stylings from "Heartbreak Hotel" to
"Instant Karma". Today,
we'd simply call this effect
"slapback echo", and it was a kinda cheesy way to
simulate
a doubled vocal take. The effect, such as it was, took
advantage of the
fact that when you record a track, there's
a slight delay between the signal
sent to tape by the
record head and that actually picked up by the sync head
-
something that you could adjust (up to a point) but
varying the speed of the
tape. Later, longer Pink Floydian
delays were achieved by recording on one
machine while
feeding its tape output into another machine across the room.
With
a few well-placed mic stands to wrap the tape around
as it went by, delays of
any length were possible!

Tape machines were great for other effects than just this,
such as
pitch-shifting, sampling, (the Mellotron!) tape
saturation and varispeed
chorusing. But perhaps the
greatest effect of all was created by Olympic
Studios
recording engineer George Chkiantz in London. This
effect, known as flanging,
is unmistakable, having
been used on countless pop hits, particularly by such
bands
as Journey ("Kohoutek"),� ELO ("A New World Orchestra") and
the
Doobie Bros ("Listen To The Music").

So how was analog tape flanging done? From Wikipedia:

http://en.wikipedia.org/wiki/Flanging

"The name flanging comes from the original method of
creation. You
start with two 3-headed tape recorders -
3 heads means one for
recording, one for playback and
one for erase - put into record mode.
You record the
same signal into both machines. The playback head
is
located after the recording head so you can hear the
actual recording.
You then take the playback-head
output from these two recorders and mix
them together,
recording them onto a 3rd recorder. Obviously, these
tape
recorders will be slightly out of sync already and
create a phasing
effect when you mix in the second
machine. In fact, the best effect is
created by
deliberately making the second machine run a fraction
faster
than the first. The effect can then be
accentuated by putting a finger
on the flange (that is
to say, the rim) of one of the tape reels so
that
machine is slowed down, slipping out of sync by
tiny degrees. A listener
will hear the familiar
"drainpipe" swooping effect as
shifting
sum-and-difference harmonics are created. When
the operator removes
his/her finger the tape speeds up
again, making the effect move back in
the other
direction. "

The pointing of bringing all of this up is that most DSP
flangers cannot
capture the true "flying through the null
point" whoosh you get with the analog
technique, because
this requires simulating the sound of two tape reels
that
actually cross each other in time as the "wet" reel
catches up with the dry one.
The other problem is that it's
often very difficult to get the peak of the
"whoosh" to
happen with plug-ins exactly where you want it to, each and
every
time you play. There are technical reasons for why
this is,� (and maybe one
day somebody will point me toward
a native-DSP double delay-line tempo-synced
flanger plugin
that does this correctly) but until then I'm going to show
you
how to you can roll exactly this effect from
scratch.

In this example, we're going to work with the finished mix
of a song and Old-Skool
a few bars in the middle, using
little more than some newfangled digital
editing.

1) Create a new empty project in SONAR and import your
stereo master,
creating a single audio track (Track 1)
that contains one long clip.

2) Clone this track and
its contents, creating Track 2. Label Track 1 "Dry"
and
Track 2 "Wet".

3) Isolate the part of the song you
want to flange (Measures 8-10, say) in
Track 2. Using
slip-editing, non-destructively crop the track's clip so
that
it contains only that section.

4) Extend the
clip you just cropped by about an 8th note before and
after,
then Apply Trimming. Non-destructively fade the
early area in, and the late
area
out.

If you play the two tracks together at this point, the only
thing you should
notice is that the song gets louder (6dB
louder, in fact) where the two clips
are playing together
but otherwise everything sounds the same. If you're
output
bus is clipping, drop it by 10dB or so to give
yourself some mix headroom. Now,
we're going to do some
magic to create the actual tape flange effect.

5) Select the cropped clip you created in Track Two and
destructively
pitch-shift it sharp (Process/Audio
Effects) by a tiny amount like +1.3
cents. Do NOT
preserve duration, and use the highest accuracy available.
A
good tool for the job is the Sony Pitch Shift plugin
that comes with Sound
Forge. You can also process the
clip as an offline edit with Adobe Audition
or Wavelab,
but the point is not to use a pitch-shifter
that
preserves length; the intent is to simulate a
slightly sped-up (in this
case) tape reel, which
naturally affects both pitch -and- time.

6) From the
cropped clip's Clip Properties dialog, increase its Start
time by
4 or 5 ticks, thus delaying it
slightly.

You're done. Play back your mix and revel in the
flange!

How It Works

Technically, what we're doing is mixing the song with a
slightly sped-up and
delayed version of the original.
Although the original dry signal (think: tortoise)
has a
slight head-start in time over the sped-up version, the wet
signal (think: hare)
will eventually overtake it and that's
when the "whoosh" happens. The
comb-filtering affect that
results as the two signals pass each other by is what
gives
you the classic analog effect.

If you want to be totally authentic, real analog flanging
involves slowing
down one reel instead of speeding
it up. And if you want to do this, (it
sounds identical)
just pitch-shift the wet clip slightly flat
(-1.3
cents) and move it a few ticks early in time.
The reason I prefer the
"speeding up" method is conceptual
simplicity; you can't move the wet clip
forward at all if
it starts at the very beginning of time, for example.
Also,
you end up saving a few bytes on disk because while a
sped-up clip is going to
be slightly shorter, a slowed-down
clip is going to be slightly longer.

"Tuning" The Beast

There are two factors that control the rate of the flange
effect; the amount
of the delay, and the amount of
pitch-shift. Shortening the delay will
make for a
faster sweep, as will Increasing the amount of
pitch-shift.
Likewise, Lengthening the delay or
Decreasing the amount of
pitch-shift makes for a
slower sweep. Since the pitch-shift operation is being
used
destructively here, your best option is to leave pitch alone
and simply
adjust the wet clip's delay to taste. With a bit
of trial-and-error, you should
be able to get the sweep to
run at exactly the rate you desire with the peak of
the
"whoosh" happening right in the middle of the clip.
(Tweakheads note: Why
not just run the Sony pitch-shift
plugin non-destructively? Because it's a
non
realtime-compatible effect and SONAR will eventually
choke.)

Note: What constitutes a "single-tick delay" is going to
vary according to
your project's tempo. SONAR, for example,
uses a default resolution of 960 PPQ
which at 120BPM =
60000/120/960 or about .52 mSec per tick. Therefore, in
this
tutorial delaying a clip by 5 ticks would be
equivalent to about 2.60 mSecs at
120BPM, or� 5.21 mSecs at
60BPM. (You're probably not going to need more
accuracy
than this.)

Now, the reason I recommended using 1.3 cents of pitch
shift here is because
it seems to represent a good balance
of DSP quality vs. sweep-rate
adjustability. Small amounts
of pitch shift are more accurately performed in DSP
than
large ones, so keeping them small makes for a smooth-sounding
effect. Heck,
even less might be better - a flange sweeping
at +.65 cents/10 ticks might sound
slightly better than one
at +1.3 cents/5 ticks, but not all pitch-shifters can be that
subtle!

(Note: The .mp3 example of the effect described here
originally appeared in the Jimmy Hats' team entry,
"Annabella".)

-djh

5 comment(s) | viewed 160
time(s) | |

Your Comments

Commented by CapnZilog - Jul 02, 2006 @
04:50:54 AM

Regarding ADT, I've since read a
description of that as being closer to the tape flange setup
described here than rockabilly slapback. When not touching the
reels at all, you still get a mild chorusing effect thanks to
the random short delays introduced by the wow and flutter of
analog tape playback.

As I recall it was playing around
with this (and the varispeed knobs) that led to the accidental
discovery of flange, which George Martin slyly referred to as
the "double bifurcated flange technique" or something like
that. ;)

Commented by Zer0fluX - Jun 12, 2006 @
09:09:32 PM

Awesome stuff.  Thanks for
sharing this technique.

Commented by Believer - Jun 13, 2006 @
03:17:26 PM

Thanks Capn! I was planning on
using this type of an effect in a song I'm working on now.
I'll have to give this a shot. Thanks for taking the time to
write this. I just got Home Studio XL and I love the
versatility and features it has.

Commented by radica - Jun 15, 2006 @ 10:52:04
AM

Great info man
thanks

Commented by VanHelsing - Jun 19, 2006 @
10:46:01 AM

Geee!! That Zilog guy never ceases
to amaze!!

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