Written by Julia Hawkins, IRENE Audio Preservation Engineer
In 2021, NEDCC had the opportunity to digitize 27 discs of the Vernon “Dr. Daddy-O” Winslow collection from the Hogan Archive of New Orleans Music and New Orleans Jazz, a division of Tulane University Special Collections in Louisiana. Winslow was the first Black radio disc jockey on New Orleans airwaves, and these recordings— originally aired on WWEZ AM between 1949 and 1958—contain a rich variety of content. As part of his “Jivin’ with Jax” program, sponsored by New Orleans’ Jackson Brewery beer company, Winslow broadcast live events, music, and interviews with local figures and prominent Black celebrities. This story covers the digitization of an interview between Dr. Daddy-O and Duke Ellington on a delaminating disc using the IRENE 2D system.
The recording medium for the broadcast show, as with many radio programs at the time, was the lacquer “instantaneous” audio disc. These discs are composed of a nitrocellulose layer applied to rigid-base materials, such as aluminum. The lacquer was soft enough to record on to directly, and durable enough to withstand several playbacks. This made them a great fit for radio professionals like Winslow, who may be recording on-the-fly in a variety of settings and only really needed high-quality playback for broadcast.
Unfortunately, these discs were not designed to last. Most of the discs NEDCC received from Tulane were too damaged to digitize using traditional playback methods such as a stylus. Even when these discs are new, the soft surface of the lacquer is especially prone to mechanical damage such as gouges and scratches. As demonstrated in this collection, discs were also purposefully “damaged” as part of the broadcast editing process. For example, rather than pressing a “delete” button, radio professionals would mark a bad track with razor blades and tape, physically preventing it from being played back for broadcast.
As time passes, the lacquer begins to deteriorate, most commonly by losing its plasticizer—usually palmitic or stearic acid. This may exhibit exudation, which occurs when the plasticizer forms a deposit on the surface of the disc. This deposit is usually white and waxy in appearance, but can initially present as a more subtle haze.
Exudation is a sign that the lacquer is decaying, and it obscures the grooves, introducing a potential source of noise. Even more problematic is a type of damage called delamination. As lacquer decays and the plasticizer is lost, it may shrink slightly, cracking, lifting, and sometimes completely separating from the disc’s base material. In the picture above, you can see that lacquer has completely chipped away in one spot at the edge of the disc and around the spindle and drive holes in its center. The way that delamination presents can vary from disc-to-disc, since the exact formulation of the lacquer could differ based on the manufacturer and even the batch.
The intact discs in this collection were cleaned and digitized with a stylus. The remaining discs were reformatted using the IRENE (Image, Reconstruct, Erase Noise, Etc.) system. IRENE uses ultra-high-resolution cameras to capture the topography of a disc’s grooves. The data is then converted into sound using computer software to analyze the images.
An IRENE transfer happens in two steps. First, the object is imaged. Starting at the outer edge of the disc, the object spins on a platter underneath the camera, which gathers lines of data as the grooves pass by. When it completes a rotation, the platter will move to the next section of the disc, where it starts another rotation under the camera. This process repeats, resulting in a series of images, or one large, compiled image file (depending on the imaging method used). Next, the images are processed using a program called Weaver. This software processes and analyzes the images to generate the audio files.
Capturing audio in this way eliminates the need to come into contact with the damaged disc surface. It also provides a little more flexibility. At NEDCC, we can choose between 2D and 3D imaging systems to get the best image possible of each disc. We can also use a variety of tools in our processing software to address different kinds of damage. Let’s look at a 2D example.
IRENE 2D EXAMPLE
One disc in the Vernon collection contains a recording of Dr. Daddy-O interviewing Duke Ellington on a 12” Audiodisc brand lacquer disc on an aluminum substrate. The disc is heavily delaminating in the two outer bands, and unfortunately, most of these pieces were completely gone, rather than simply detached.
In many cases, when discs with this kind of damage come to NEDCC, we are able to puzzle the detached pieces back together before imaging. With this disc, we had to work with the losses and recover the content that remained.
We decided that the 2D imaging system was the best option to scan this disc. The 2D system uses a line scan camera to take high-resolution, magnified grayscale images of the grooves. This camera is mainly used for discs with laterally modulated grooves (grooves that wiggle from side to side). Most discs fall into this category, including the discs from this collection.
In the above screenshot of the grooves from this disc, the skinny white line is the groove bottom, and the black section is the walls of the groove. Weaver processes 2D images like this using an edge detection algorithm that uses the contrast between the white of the groove bottom and the black of the groove wall to determine where it should place the data points that will become the audio file. You can see that the surface of the disc (the area in between the grooves) has suffered wear and tear, but the contrast of the groove bottom is consistently present. In cases where the groove bottom is extremely worn, we can use the 3D imaging system instead. The analysis of these images uses the whole curve of the groove, rather than the groove bottom, and can produce better audio in these instances. This was the case for some other discs in the collection.
To process this disc, we compiled the images into two large chunks. The first consisted of the first two bands, including the large loss, and the second contained the mostly intact, remaining bands.
When processing images in Weaver, there are two main operations to perform. The first is called tracking. Simply put, tracking uses the characteristics of the image to locate the audio, ideally the groove bottom we identified above. The more accurate the track, the better the final audio will be. On an intact disc, tracking usually happens automatically, with some minor parameter adjustments.
For a disc with losses like this, the software needs a little help. We use a process called “manual tracking” to edit the track as it is created. This helps the track properly bridge gaps and move in the right direction if the grooves are misaligned (as they often are when a disc is broken or delaminating). If an object is damaged, there will be evidence in the resulting audio, no matter how accurate your track is. However, by carefully monitoring and editing a track as needed, we can ensure that the recording will be as complete and contain as little noise as possible.
Once the correct path through the grooves has been located, Weaver processes the image by measuring the displacement of the groove with respect to its unmodulated path along a sequence of points and accounting for the velocity of the stylus at each point. A few calculations later and voila! We have an audio file.
In the first two bands, it is difficult to understand what Dr. Daddy-O and Ellington are saying, which isn’t surprising, since the loss affects almost half of each rotation. There is enough content, however, to catch bits and pieces. Luckily, once the whole disc was processed, it became clear that the second set of bands were actually a duplicate or at least a second take of the content from the first set of bands. It seems like maybe Winslow was an early adopter of LOCKSS (Lots Of Copies Keep Stuff Safe).
The 27 discs digitized at NEDCC are only a small portion of the more than 3,000 recordings created during Winslow’s time at WWEZ. Even in this small sample, his skill as a broadcaster shines through. He works the crowd at live events, he banters with interviewees like they are old friends. There is a real sense of ease and joy captured in many of these recordings that, thankfully, were not lost to time and deterioration.
Recordings of the Vernon "Dr. Daddy-O" Winslow collection are currently available via Tulane University’s Digital Library: https://digitallibrary.tulane.edu/islandora/object/tulane:vernonwinslow.