The editorial principles of the Schumann letter edition follow the guidelines the „Arbeitsgemeinschaft Musikerbriefe“ within the professional group „Fachgruppe Freie Forschungsinstitute in der Gesellschaft für Musikforschung“ has set concerning the edition of musician's letters. The „Arbeitsgemeinschaft Musikerbriefe“ was founded in 1994 subsequent to a colloquium in Mainz about composer's letters of the 19th century. On this occasion, Gerd Nauhaus had already pointed out that an „extensive edition of Schumann's letters“ was long overdue.
The Schumann letter edition is based on the surviving originals. Where these are not accessible any more, it is rested upon secondary sources like transcriptions, printed publications or drafts (like in the „Briefkonzeptbuch“ BK). In the event of a letter having already been published, the first publication and the four „classical“ Schumann editions by Wilhelm Joseph von Wasiliewski („WRS 1858“, „WRS 2/1869“, „WRS 3/1888“), Clara Schumann („Jugendbriefe 1885, 4/1910“), Gustav F. Jansen („Briefe NF 1886“ and „Briefe NF 2/1904“) and Hermann Erler („Erler I,II“) are named, other publications are only mentioned in case they're not related to these sources.
If a letter exists only as a transcription or in an edition, the most complete and reliable source is always the basis, versions that vary from this source are singularized and critically commented. For Schumann's letters, the so-called „Briefverzeichnis“ („BV-A“ and „BV-E“), in which Schumann used to list most of his posted and received letters from the mid 1830s onwards, is consulted as an extra source. Schumann's short summaries in the BV-A are attached to the particular letter.
Occasionally there are differences between the age determination of a letter and the actual date in the letter index. In this case, the date of the corresponding entry is quoted.The business notes of the „Neue Zeitschrift für Musik“ and the recensions and advertisements up to 1844 form other sources.
All the letters which are scheduled in the letter index get their own number in the edition of the particular letter exchange, even if the text itself has to be considered as lost today, whereas letters whose former existance is not ascertained do not get a number. In case several letters which have been written within a certain timeframe are missing, there is a summary note in the preface of the actual volume.
In the headlines of the individual letters, the recipient and the destination as well as the forwarder, the original location and the date are indicated. In case these indications are missing in the original sources they are a case of editorial complement and Schumann's letter indexes may serve as a basis in many cases.
In the case of letters originating from insitutions such as publishing companies, the writer is identified through comparing the different handwritings and his name is postpositioned in brackets. If letters of institutions which were corresponding with Schumann like the „Neue Zeitschrift für Musik“ or the „Allgemeine Musikverein zu Düsseldorf“ are registered in Schumann's letter indexes they are included in the correspondence even if they're not addressed to or written by Schumann himself.
As far as there are autographs which could be dissected, they are described in the comment. Inscriptions by the addressee or later possessor are as well quoted there, if necessary slashes serve as indication for the alignment. If the origin is clear, older library signatures remain unmentioned. Insofar as there are readable postmarks, the first and the last one, usually concerning departure and release of the letter, are quoted.
The reproduction of the text follows the source's original orthography, only distorting mistakes are corrected. A differentiation between German and Latin script is dispensed with.
In most cases, German script dominates in the autographs, for foreign words, names, titles and instrument information Latin script was predominantly chosen. Continuous Latin spelling of singular text passages is pointed out in the description of the autographs. Typical idiosyncrasies of the German script are adjusted to the German blockletters. Double dashes in compund words are displayed as single dashes („Triple-Concert“ instead of „Triple=Concert“).
The so-called „Faulenzerstriche“ above the ms and ns are dissolved and written as double consonants. Furthermore, the inverted commas which Schumann often used at the end of a word or quote at the bottom („Flamin„) are applied according to today's orthographic standards.
Dots which indicate abbreviations are maintained. Abbreviations as well as short forms which appear in the documents several times and are, according to the „Duden“, still in use today are not dissolved but can be looked up in the abbreviation catalogue in the „Dokumententexte“. The dissolution of other abbreviations is written in square brackets. The contemporary scripture used lots of logograms, so-called abbreviations, praticularly on coins. Insofar as a transcription into letters is not easily possible, the logogram is written in historic script and designated as abbreviation in the apparatus.
The spacial structure of the autographs is displayed schematically, title page designs and similar combinations are transferred according to the diplomatics. All breaks are displayed as in the original and are indicated through indentations.
The endings are displayed following the original, either left-adjusted or in a standardized distance from the right margin. In the text itself the original alignments are not marked, only the pagebreaks of the autographs are emphasized in the continuous text (including the indication of the following page). Subsequent insertions are exposed. Provided that it isn't noted differently, such insertions are placed above the line. All other postscripts appear at the end of the autographs in hypothetic order.
In case they do not follow the complementary close and the signature but are noted on the margin crosswise, their position and direction of writing are named in the annex. Datelines and comments concerning the forwarding of the letter and eventual enclosures are rendered single-lined. In case it's not a head address, the address, displayed according to the diplomatics, is placed after the actual letter. In the event of there being no address, one may suggest that the letter has been sent in another envelope which is now missing.
 Bernhard R. Appel / Joachim Veit, Richtlinien-Empfehlungen zur Edition von Musikerbriefen, Mainz 1997 (http://www.adwmainz.de/fileadmin/adwmainz/MuKo_Publikationen/richtlinien-musikerbriefe.pdf).
 Gerd Nauhaus, Aspekte der Schumann-Briefedition, in: Komponistenbriefe des 19. Jahrhunderts, hg. von Hanspeter Bennwitz, Gabriele Buschmeier und Albrecht Riethmüller. Mainz/Stuttgart 1997 (= Akademie der Wissenschaften und der Literatur. Abhandlungen der geistes- und sozialwissenschaftlichen Klasse 1997 Nr. 4), S. 63-73, hier S. 71.