Rediscovering Bach was an event of some importance and the first step in a very long road that is still being followed today. This road was not exempt from difficulties, in that the revival of early music implies confronting the almost unattainable objective of recreating its original sound, which requires an exhaustive knowledge of each and every factor contributing to its performance. Unfortunately no record of the actual sound of music existed prior to the invention of the phonograph in 1877. The closer the repertory to be revived in time, the greater the probabilities of accuracy. Moreover, from the mid eighteenth century onwards, with the main exception of aleatory music, a musical score became a finished artistic product in which each and every musical parameter is indicated, although there is always room left for the performer’s own sensitivity in its interpretation. Illustrative of this is the often-repeated anecdote of the premiere, in May 1824, of Beethoven’s Ninth Symphony, which the composer himself, already completely deaf, attended. Called upon to acknowledge the audience, Beethoven is said to have had no alternative but to reprimand the performers: while they were performing he had been following the score himself, but when the orchestra and choir performed the last chord of the work he still hadn’t finished reading it. Truth or part legend, it would have been practically inconceivable to Beethoven that any of his works could be subject to even the slightest manipulation, unlike composers of previous generations, Johann Sebastian Bach among the greatest.

Despite the fact that Bach and the composers who followed him never stopped setting the basic parameters of their own works, he did make at least two exceptions to this rule, leaving one of the essential elements of a composition open to the performer: timbre. This is the case throughout most of The Musical Offering (BWV 1079) and The Art of Fugue (BWV 1080), both works susceptible to being performed by instruments of a varying nature. Despite this practice being backed up by a long tradition, during this period the composer’s attitude was very different to that of previous centuries. For example, after setting the subtlest of his poems to music, the best a troubadour could hope for was that in its oral dissemination his melody would gradually be varied to the point that it was occasionally transformed into another melody altogether. In general terms, it was not until shortly prior to the fourteenth century that there was evidence of the composer’s interest in trying to fix the result of his creation. While artists such as Guillaume de Machaut (ca.1300-1377) began to get annoyed by someone taking the liberty of altering his compositions, others such as the lutenists and vihuelistas of the Renaissance took less offence, converting their works, once written, into sound forms to be completed by the performer. How this should be done, which version of a troubadour fragment conserved in various sources should be chosen, which instruments should be used in the accompaniment to a fifteenth-century song, are just some of an endless number of questions derived from open musical documents. These are the testimony to other periods of music whose sound world can only be reconstructed using relative approaches. There is no reason for their veracity to be any different to that of a Beethoven symphony performed at the tempo indicated by the composer. His symphonies are works just as fixed and complete as a painting displayed in a museum, while that of a medieval or early-renaissance artist is a work that in many cases permits more than one interpretation.