cf:

In music, primary sources are first of all the scores—scores as nearly as possible in the form that the composer left them. In a study of performance, records [or any recordings] are also primary sources. Other kinds of primary sources are letters of a composer; an autobiography or a biography written from personal acquaintance and not from other writings; articles in newspapers and magazines from the time of the events reported— also criticism, programs, advertisements, etc. (In some cases, notably Bach, Handel, Mozart, and Schubert, such materials have been assembled and gathered into “documentary biographies”—this does not take away from their value as source material.)
http://www.elmhurst.edu/~markh/history2/FullerPapers.htm

consisting of reports and notes from 17th century inventories of archaeological remains and historical monuments. These inventories are of significant value as source material for archaeologists and art-historians.
http://www.kb.se/HS/Eng/Aldre.htm

Philological study of the source texts is necessary to establish their date and nature as texts, and thus their value as source materials for the historian.
http://www.umass.edu/wsp/methodology/philology/summary.html