Zen and the Art of Tape Editing

Article by Scott Edwards

Scott Edwards is best known these days as the head of the Guthrie sound department and a very accomplished sound designer. I first met him in the early ’90s at Penumbra Theatre where he was, indeed, putting together sound designs using two or more reel-to-reel tape decks and multiple cassette decks to create complex soundscapes. In this article, he shows us that even though we may have fond memories of the past, we should never go back. ——Mike Wangen

When I started my career in sound design, we were in the golden age of analog tape. This was in the early 1980s and tape was king. The technology had matured and the open reel tape machine was the standard recording and playback device in production audio. These days, one rarely sees or uses an analog tape machine; their use is relegated to playing back existing analog tape masters, mastering by diehard analog enthusiasts, or just gathering dust in storage closets. In what seemed like a blink of an eye, they became all but obsolete and forgotten.

Although the advent of the digital audio workstation has made my life as an audio designer much easier and productive, I do have many fond memories of thousands of hours spent editing tape. I thought I’d pass some of these on to the “digital” generation who may not have had the pleasure.

My first assignment as an intern in the audio department at the Children’s Theatre Company was to edit a “safety pancake” or “safety dub.” Now, at that point in my career, I really had no idea what that was—and not much of an idea of how to edit it either. Someone handed me a grease pencil and a razor blade and pointed me at the nearest tape machine.

Before I go any further I should explain some basic “tape” terminology:

  • Tape: The recording medium. Audio tape is a long strip of acetate plastic coated with a magnetizable compound made from ferric oxide. In the professional audio world, tape came in  ¼”, ½”, 1” and 2” widths. Generally, in a reel size of 10½”, that’s 2,500 feet of tape—or about 33 minutes at 15 inches per second (IPS).
  • Tape machine: The device used to record and playback audio tape. The three types in use are the open reel machine, cassette tape machine, and 8-track cartridge. For the purposes of this article, we will be talking about the open reel machine. The basic layout of the open reel machine has not changed since its invention in Germany by Fritz Pfleumer in 1928. It consists of two reels, side-by-side, with erase, record and playback heads, with a head stack between them. On the left is the supply reel; on the right, the take-up reel. Between the head stack and the take-up reel is the pinch roller and capstan. Tape travels from the supply reel over the heads, through the pinch roller, and capstan and is wound on the take-up reel. The reels and heads are not enclosed, such as in the case of the cassette tape or 8-track machine—hence the name “open reel.”
  • Capstan and pinch roller: The capstan is a machined cylindrical shaft directly driven by a powerful electrical motor. The pinch roller is a free-spinning, rubber-coated wheel pressed against the capstan shaft. The tape passes between the two and, when the pinch roller is pressed against the rotating capstan, it pulls the tape along. This mechanism is directly responsible for the speed of the tape and therefore must be precisely controlled, otherwise you will have variances in pitch. The supply reel motor exerts drag on the tape creating the proper tension of the tape against the heads. The take-up reel motor makes sure that there is no slack as it reels up the tape.
  • Wow and flutter: The measurement of speed variation in the tape speed.
  • Tape heads: Erase, record and playback. Tape heads are transducers that either convert electrical signals to magnetic fluctuations (or vice versa). The recording head imparts this fluctuation on the passing magnetic tape; the magnetic particles on the tape are rearranged in patterns that match the flux created by the recording head. The playback head transduces this flux pattern back into an electrical signal as the tape passes over it. The erase head is similar to the recording head, but simply realigns the magnetic particles on the tape back to their neutral state.
  • Pancake: Bulk tape wound on a hub with no reel flanges. You would purchase tape this way and then wind it onto reels when fresh tape was needed. Archives are typically stored this way also.
  • Heads out, tails out: Refers to which way a reel of tape has been wound. Heads out would be when tape has been re-wound onto the supply reel. Tails out, when wound onto the take-up reel. General practice is to store tape tails out since this reduces the effect of “print through.” That is, the magnetic flux on the tape can slightly alter or “print” on the layer below itself in the tape pack. This imprint can create a pre-echo or post-echo depending on whether it is stored heads or tails. The post echo effect is much harder to discern, so tails out is the preferred storage method.
  • Splice tape: Adhesive tape used to connect or splice two pieces of audio tape together.
  • Leader tape: Plastic or paper strip in the same size as the audio tape it is used with. Used at the head and tails of the reel to provide enough tape to wind on the reels before the audio tape starts. It’s also spliced between cuts of audio tape to demark cues. We generally used the plastic tape for the head and tails and paper tape for the cues as one could write the cue name on the paper.
  • Dub: Shortened version of the word “double” which in the audio world can mean to make a copy, add a track, re-record (over-dub) or add sound or dialog to an existing recording.
  • Safety dub: Copy of a master tape for backup purposes.
  • Scrub: Moving tape over the playback head either by hand or with a jog wheel or handle. This allows the operator to hear the audio very slowly so they can pinpoint it on the tape.
  • Editing block: Machined block of metal (much like a miter block) used to cut wood at precise angles. The block will have a longitudinal groove the width of the tape it is designed for and generally two angle slots—90 and 45 degrees—to guide a razor blade. On tape widths up to 1”, the 45° cut was preferred. The angle helped the splice transition over the tape heads without catching and tearing the splice.

Okay, back to the editing.

I had my tools and supplies to edit: Razor blade to do the actual cutting, grease pencil to mark the tape, splice tape, edit block, and leader tape. I threaded the safety dub onto the tape machine and rewound to the top of the reel. I played the tape until I heard the beginning of the first cut. The next step was to gently rock the reels back and forth or scrub the tape until you just heard the start of the audio. Now the grease pencil: make a small hash mark on the tape right over the playback head, which was the head farthest to the right on the head stack. This was the “cut” mark. Now draw the tape off the head stack pulling from both reels and press it into your edit block. Slide the tape until the mark was just to the left of the 45° guide. Now slice the tape with your (very sharp!) razor blade. Your first cut!

Now slide the tape pieces apart slightly and place the start of your leader tape into the block. Make a new 45° cut on the head of the leader tape and butt it up to the right hand piece of tape.

This is where things got a bit fuzzy for me: Did one put splice tape on both sides of the tape?

Yes, thought I!

Wrong, wrong, wrong. Splice tape is only needed on the outside of the tape, the non-oxide side. I only found this out after I had finished the entire reel…

To complete a splice, you would hack a 1” piece of splice tape from a scotch tape dispenser (worked perfectly to dispense splice tape), place 1/16” or so of the splice tape on your razor blade and then using the razor blade, position the splice tape over the two pieces of tape in the block. It was important to make sure there was no gap between the two pieces you were splicing together because, if there was, the adhesive of the splice tape would be exposed and would stick to various parts of the tape path—often with disastrous or hilarious consequences, depending on your point of view.

Press down on the splice tape and pull the razor away. Smooth the joint with your finger. Now pop the completed joint out of the block. Pull about a foot of leader tape from your handy dispenser and put it in the block. Cut at the 45° angle and then splice to the left-hand piece of tape still in the block. Now you have inserted a paper leader into your reel. Write the name of the cue on it with pencil and pop the tape from the block. Use the supply and take-up reels to gently pull the tape back onto the machine.

Do all this about 40 more times and you would have completed editing the reel. I remember it taking me quite some time to do this, but after a few weeks I grew quite proficient.

The editing of music on tape needed a higher order of skill. This was truly “destructive” editing because once you committed to a cut, that was that. There was no undo option. Management of the cut sections was also a bit tricky. If you cut 20 seconds of a song, that would equal 300 inches of tape. Keeping track of outtakes consumed lots of wall space and labeling was difficult. This type of editing usually involved a function on the tape machine called “dump edit” mode. This was a way to dump the tape from the machine while playing it over the playback head but instead of it going onto the take-up reel, it dumped onto the floor. (Hence the colloquialism from the tape era, “ended up on the cutting room floor.”) To do this, you would mark your cut at the beginning of the section you wanted to dump then make your cut. Now thread the tape from the left side of the cut across the heads and through the capstan/pinch roller. Hit “dump edit” and the pinch roller would engage and start playing the tape with the tape—unconnected to the take-up reel—would stream onto the floor. When you reached your out mark, you’d mark, cut and splice the take-up reel end back on. You could either throw this excess tape away, save it, or edit it back into another section of the score. It was the analog equivalent of cut-and-paste.

Another editing skill was creating the tape loop. In sound design, this was a very important skill and something you would use on every project. Looping is a common concept: Short sound or sounds repeat over and over to create a longer sound. The term “loop” comes from creating a loop when ends of tape are spliced to beginnings. For example, say you had a 3-minute recording of crickets and you need 15 minutes to cover a scene. You would create a tape loop of the three minute cut and play it five times through. In practice, we would play the loop on one machine and record onto another machine, usually a cassette tape machine or a DAT machine.

Playing a tape loop on a tape machine was very tricky. The method is simple: splice the ends of your tape loop together to form a continuous loop of tape. Thread the tape around the supply-side tension arm, across the tape heads and through the capstan and pinch roller. To play the loop, put the machine in dump edit mode. Now the pinch roller will pull the tape across the heads and since it is a loop, it will just keep going round and round until you stop it. The tricky part is managing the amount of tape in the loop. If it was a very short loop, say three feet long, there would be no problem. The loop would not even reach the floor and would just circle around. But, three feet of tape at 15 IPS would be a sound of 2.4 seconds. Not very useful.

Now take our three minutes of crickets: At a tape speed of 15 IPS, that three minutes of crickets would be 225’ of tape! So what to do with all that tape? You can’t just let it dump on the floor as it would, in short order, snarl. The solution is to stretch that tape all the way out to form a gigantic loop. This would involve several straight mic stands to act as tape guides. The loop would go out of the sound booth, down the hall, around a stand or two, back into the booth and back to the tape machine. Occasionally we would have to go all the way out the booth window, over the theater seats, to the stage and back. Now imagine if we were mixing three or four tape loops at once! This often resulted in snarls and ruined tape if something got snagged. Storing the loops was another issue since they tended to take up a lot of wall space and would inevitably get twisted up in knots.

Contrast all this with how fast and easy it is to loop a sound file in a digital audio workstation, and you will see why tape was so quickly made obsolete in the production world. One word: Efficiency.

Now that you know a little about tape editing, go out and find a tape machine and try your hand at it. It will make you appreciate your DAW just a little bit more.