2. Introduction

Safeguarding of audio recordings in the long term is a task that requires highly complex strategic and technical measures combined with sufficient financial resources. Ethical and technical principles have been laid out by IASA in the document: IASA–TC 03 The Safeguarding of the Audio Heritage: Ethics, Principles and Preservation Strategy. This document explains that preservation of audio content in the long term can only be achieved by successive migration of contents in the digital domain, and sets out consistent digital archiving principles. Digital Mass Storage Systems (DMSSs) have proved viable tools to fulfil these aims, providing at the same time new dimension of access, an attractive feature especially for broadcast and national archives. The great challenge of the present time for sound archives is the well organised transfer of their holdings, be they analogue or digital, into DMSSs, or, before these become affordable, into a pre-DMSS environment fulfilling digital preservation principles. It should be recognised that working in a digital preservation environment requires a custodial approach which is significantly different from the established role of the archivist working in the analogue world. The logistical and technical implications of digital preservation are considerable, and archivists must be aware these challenges can only be met by adequate funding.

The document presented here should assist sound archives in establishing a consistent strategy by advising on selection criteria for the prioritisation of transfer projects from different perspectives. A third document under preparation by the IASA Technical Committee will contain operational guidelines for the transfer of analogue and digital holdings into DMMSs.

In comparison to print media, audio recordings, like all audiovisual documents, require a higher degree of physical integrity than text documents. While the latter have a comparatively high degree of redundancy - a speck of mould, generally, does not render a text unreadable - audiovisual documents are analogue representations of physical phenomena (light, sound). Every detail of an audiovisual document is information and, therefore, greater care needs to be taken to maintain the physical integrity of the carrier.

Additionally, due to their chemical composition, which is sometimes highly complex, audio carriers are inherently unstable, comparing unfavourably with the average stability of analogue textual documents. With increasing development and sophistication, the technical platforms developed for audio carriers have ever shorter life expectancies. Additionally, being machine readable documents, the retrievability of the signals embedded in audio carriers is dependant on the availability of dedicated hardware, and sometimes software. Thus, even if carriers remain in playable condition, the retrieval of the recorded contents may be impossible, due to the unavailability of dedicated replay equipment. This obsolescence of formats and systems is, potentially, the great danger inherent in some of the modern digital carriers, while carrier instability is the more general problem with more traditional media.

Consequently, audio archivists are facing considerable problems in attempting to preserve the original carriers placed in their care, because in the mid- to long- term there is a major risk that carrier degradation combined with playback obsolescence will defeat the efforts of archivists to ensure the survival of the content in their care. Around 1990 it became clear that the only viable method of preserving audio contents in the long term is by transfer into the digital domain, and subsequent migration to new formats whenever the need arises. Automation was recognised as a key strategy in optimising the associated workload. This led to the concept of Digital Mass Storage Systems (DMSS), which automatically monitor the data integrity of their contents, copy endangered carriers to new ones before they become unreadable, and migrate the whole archive into a new system once the old system is threatened with becoming obsolete. DMSSs have been introduced over the last ten years and have become state-of-the-art in audio archiving.

Such systems enable the long-term preservation of content, and also provide, as a by-product, a powerful new means of playback access. For the first time in the history of many collections, contents would be easily accessed from the desk of radio journalist or from the visitor’s booth of library clients.

Digital Mass Storage Systems are equally important as target repositories for the safeguarding of analogue material, still the greater part of many sound archives’ holdings, as well as for digital holdings, generally kept on consumer formats of questionable carrier and/or format stability. Consequently, this paper equally deals with analogue and digital carriers.

Because the transfer of holdings to DMSSs is an elaborate and time consuming process, it is crucial to establish meaningful hierarchies within the sound collections to be transferred. Audio archives can rarely afford "factory style" transfers as envisaged by relatively well-resourced radio archives. This approach may be feasible if the originals are of uniform character, and of high technical quality. Most heritage collections, because of their heterogeneous nature, do not lend themselves to such semi-automated transfers, nor can the respective institution usually afford the large investment needed for such kind of quick and total transfer, because of the considerable costs of equipment and personnel. Because conventional, operator monitored transfer is extremely time consuming (one operator needs at least 3 hours for the transfer of one hour of original material) and because budgets of heritage institution are notoriously low, transfer of holdings into a DMSS will last years, if not decades. A clearly defined hierarchy of priorities for digitising is imperative to avoid, for example, stable materials being transferred first, while in the meantime unstable materials deteriorate to the point where they become irretrievable.

The prioritisation of archive material for digitisation will depend on the statutory obligations and business objectives of the archives. National sound archives will normally have legal deposit responsibilities, and must together with research archives comply with the needs of scientists and researchers. The significant selection criteria for broadcast archives are the possibility of reuse of the material in programme production. Generally, archivists are reminded that according to archival principles neither digitised originals nor non selected original materials should be destroyed. The selection may thus involve a policy decision on keeping the originals for later consultation, or offering them to other archives for further preservation.