# Reading Tapes Backwards: A Legitimate Approach to Saving Time and Money in Digitization Projects?
## 5 Conclusions  
This article was motivated by the open question of whether digitizing tracks in opposite directions on the same magnetic tape is a viable solution for audio preservation projects, and in particular whether it is compatible with a sound theoretical and empirical methodological approach to preservation. The first step to answer this question was to build a data set that would help determine whether it is possible to identify _and_ measure the differences between signals that were picked up in the intended direction ('forwards') and in the opposite direction ('backwards'). Seven audio excerpts (including music, voice and reference signals) were recorded on a magnetic tape. Then they were played back and digitized ten times: five forwards and five backwards. The obtained 70 audio files were compared by means of the Normalized Euclidean Distance, a feature specifically defined to quantify the differences between audio signals. The results show that the distance between the files obtained by reading the tape with the same direction (congruent) is significantly more minor than the distance between files obtained by reading the tape in the opposite direction and reversing them in the digital domain (non-congruent). These results support the idea that the practise of reading tapes backwards introduces measurable alterations in the signal. These alterations are grater than the variability that is inherent in the playback process with analog reel-to-reel tape recorders. It is important to observe that the introduction of said alterations does not imply that reading tapes backwards (in the context of digitisation projects) is wrong or should be avoided. It means that we should be aware that the two approaches (forwards and backwards) do not yield the same results, at least at a signal level. This means that the decision about whether it is convenient _and_ safe to save time by reading tapes backwards should be evaluated case by case. The analyses conducted on the audio signal in this study do not inform us about the subjective perception of the alterations, that is, whether a human listener could tell the difference between the takes. This aspect was not included in the scope of this study, but we plan to make it the center of a future study. The goal of audio preservation is not only to support future signal analyses, but also to prepare audio material for humans to listen to. Therefore, the listening experience is a relevant aspect in the broad picture of this study, of which the next steps are:  
1. the reproduction of the experiment presented in this article on different equipment, to assess the influence of the playback machine on the differences observed in the signal;
2. a perception test where human listeners evaluate the signals digitized forward and backwards, in order to evaluate the differences found in the signal against the impact they have on the actual listening experience. On a final note, audio preservation is a well established field. However, with the ongoing research presented in this article, and the authors' other scientific productions, we show that this is a field with many open questions, which greatly impact the theory and practice of preservation, and which need to be addressed with the scientific method and small, incremental steps forward. Of equal importance is to \"bring the science\" to a field that has existed outside of academia and in tight connection with industry for many decades before becoming of scholarly interest, formalizing the questions and exploring them with a scientific approach--while at the same time not ignoring the information and knowledge present within the expert community of audio veterans and industry people, however hard (and ever harder) it is to retrieve, gather, verify and interpret. Conceptualization F.B. and A.R. ; Methodology A.R. and E.M.; Software A.R. and E.M.; Validation, A.R. and E.M.; Formal analysis A.R. and E.M.; Resources V.B. ; Data curation by E.M.; Writing--original draft preparation, F.B., A.R., E.M., V.B. ; Writing--Section 4.1, R.L.H.