Recovering the Unrecoverable Panel

Play it again - Recovering analog audio from degraded tapes using a synchrotron x-rays.

The Magnetic Tape Alert Project has identified millions of audio and video tapes containing unique recordings that are in urgent need of digitization. About 30% of these tapes are suffering from degradation, which can prevent their digitization using conventional playback equipment, in which the play head is in physical contact with the mechanically tensioned tape. Compounding the issue, original hardware and spare parts are becoming significantly harder to find.

At the Swiss Light Source of the Paul Scherrer Institute in Switzerland, we use synchrotron X-rays to investigate magnetic materials. Based on X-ray spectroscopy, we are developing a unique non-destructive readout method for the recovery of audio signal from magnetic tapes using circularly polarized X-rays by exploiting the X-ray magnetic circular dichroism effect. Our method reads out the magnetic information stored on the tape without contact. This is in stark contrast to a play head, which touches the tape, placing it under mechanical stress. In addition, we digitize the raw signal, exactly as it is recorded on tape (magnetic signal). Whereas play heads sense the magnetic field (derivative of the magnetic signal stored on the tape), which needs to be processed by dedicated electronics to reconstruct the audio signal. Thus, our method preserves the tape mechanically, and extracts the raw audio signal before equalization. In collaboration with the Swiss National Sound Archives, we have established the possibility of reading out analog signals from ¼-inch tape. Furthermore, we successfully demonstrated signal recovery from artificially aged and damaged tape as well as from tape with sticky shed syndrome (without baking).

While proof-of-principle results will be presented for segments of ¼-inch tape, further development of the technique will allow the recovery of entire tapes with high resolution in various multitrack formats using the same equipment, eventually remediating the need for original readout equipment

• Sebastian Gliga is a physicist at the Paul Scherrer Institute in Switzerland. He grew up in Canada and earned his PhD in Germany, working on nanomagnetism. He currently uses X-rays to study the magnetic properties of materials at the nanoscale — tens of thousands of times thinner than a human hair.

Sebastian’s passion for recorded audio was sparked by his mother, a musician, and is grounded in physics. He leads the development of an X-ray based technique to recover signals from magnetic tapes and collaborates closely with the Montreux Jazz Digital Project (Switzerland) and the British Film Institute (UK) on preservation efforts.

Sebastian has held research positions at Argonne National Laboratory (USA), the Max Planck Institute (Germany), and ETH Zürich (Switzerland), and has published more than 65 peer-reviewed papers.

For years, before analog tapes and after digital cassette like DAT, were used to record music. For a short time DATs were also implemented as archive media. Today we have to deal with some difficulties when reproducing these magnetics carriers and we are faced with different problems present like mold, layers glued together, tape wrinkled by a faulting mechanism and syndromes like high level of vinegar syndrome.

Is there a solution for recovering these recordings?

In this presentation, Gabriele will show you when he was able to fix the problem and when he wasn’t!

The IRENE project is a collaboration between Lawrence Berkeley National Laboratory and the Library of Congress to develop imaging systems to capture and reconstruct sound from recordings with the signal cut, etched, drawn, etc. into or onto the audio media. With over 20 years of research and development, IRENE Systems that image in both 2D and 3D have been produced. Imaging in 2D is faster but acquires less signal information and can only reproduce audio from recordings with lateral motion. The 3D systems utilize a confocal probe that captures the full groove profile making it well suited for both vertically and laterally cut grooves. This technology has chiefly been used to preserve sound from highly fragile and degrading media, often on historic formats. Because the imaging capture process does not physically contact the grooves and the system can be configured to accommodate gentle mounting and movement of the media while being scanned, “irretrievable” recordings have been preserved utilizing this technology.

The process of imaging audio media does not introduce any ringing or harmonic distortion to the playback of the signal, which results in extremely flat representations of the signal far beyond human hearing. It is however very susceptible to the media’s roughness and any particulate matter that can’t be cleaned from the media, which then manifests as noise in the audio domain. Machine learning and AI training have been explored as a method to model the sound of stylus playback and reduce noise artifacts. The widespread development of AI powered tools for audio restoration are of particular interest to this project and are being explored and followed closely both for their usefulness in extracting sound from images and their impact on preservation practices enlarge.

This paper seeks to revisit traditions of radio performance and ‘features’ as they once flourished at the ABC throughout the 1970s, 80s and 90s. These traditions risk being almost entirely silenced or forgotten in the ABC’s history due in part to ongoing weaknesses associated with the current archive (NAA and ABC collections), including access restrictions and the limitations specifically of the metadata of the Radio Program Archive. Responding to the themes of this year’s conference, the sound archives of the ABC may well be endangered if they remain as analogue magnetic tape recordings, but if they cannot be easily located and re-sounded for researchers and wider publics, they risk another and just as decisive road to oblivion. By focusing on one program I produced independently for the ABC in 1996, and its sounding and silencings in the collection, I hope this presentation can offer a small opportunity to re-connect to the larger hidden history of ABC radio and its traditions of cultural and literary production which characterized the national network, now ABC RN, until the early 2000s, and yet are barely audible today. This presentation involves re-play and recital of Antonin Artaud’s infamous and censored work, ‘To have done with the judgement of god’ (recorded 1947 ORTF, France, first broadcast ORTF 1973), and the recounting of three distinct archival interventions (ORTF 1947/Farabet 1973; ABC, Madsen 1996; and Bandcamp, Madsen 2025) across time and continents. This recording’s history and presence in the ABC and NAA’s archives as a recovery and as an annotated broadcast of a work which still disturbs and even shocks audiences, is of great interest in and of itself, but here it might also alert us to the role played by the ABC as safe haven for material and artists, thinkers and performers that might be considered risky or radical – certainly unorthodox. This re-sounding of one ‘monster’ of a recording in the history of radio speaks to an obscured part of our national radio story; it also delivers that repressed and singular voice from the vaults, silenced but now freed to be encountered and comprehended anew, communicating with as much sense as non-sense

• Dr Virginia Madsen is a senior lecturer in media, and former director of the Centre for Media History, Macquarie University. Prior to her academic career she was a founding producer of the ABC audio arts and performance program, The Listening Room. She has created a large body of diverse radio and sound works, including for new audio media platforms. She has published widely on sound culture, and public broadcasting, its forms and history. Current writing and book projects focus on the international expression of a documentary imagination in sound from early radio days to podcast, and a portrait of the cultural network and institution, ABC Radio National (informed by detailed archival and comparative research plus oral history interviews).
  Recent chapter contributions appear in Listen Up! Radio Art in the USA (Transcript, 2025); Word, Sound & Music in Radio Drama (Brill, 2024); This is Channel Earth: One Hundred Years of Global Radio Play (Brill/Fink, 2024); Le désir de belle radio aujourd'hui (fiction, documentaire) (Presses Universitaires de Rennes, 2024).
  Experience her sonic portrait/locative media Soundtrail for the town of Portland, NSW on site or via web (launched 2023): soundtrails.com.au/portland-nsw/
  Profile: researchers.mq.edu.au/en/persons/virginia-madsen