Opus numbers with “a” and “b” in Kuhlau’s music pieces

There are opus numbers with “a” and “b” appended in some of Kuhlau’s works.

These alphabet characters were added not by Kuhlau but by Dan Fog who published "Thematic-bibliographic Catalog" in 1977. These are seen more in his earlier works (those with smaller opus numbers) but it is not for certain the criteria in which Dan Fog decided to put these characters after the opus numbers.

  Composed Published Page Instrument
5a ca.1811-12 1812 23 Piano Sonata
5b vor 1806 ca. 1806-07 8 Lied
6a ca. 1811 ca. 1812 47 Piano Sonata (3 Works)
6b 1811-12 1812 11+5 Piano Sonata with Violin ad libitum
8a ca. 1812 1814 31 Piano Sonata
8b ca. 1810 1810 11 Piano Sonata(for 4 Hands)
10a ca. 1813 1814 19+16 Flute Duo
10b vor 1810 um 1810 29 Flute Solo
11a 1812 1814 22 Lied
11b ca. 1810 1810 9 Lied
72a ca. 1826 1826 15 Piano Variation(for 4 Hands)
72b 1821-23 1823 9 Lied
98a 1829 1829 11+4 Flute and Piano
98b   1834 9 Piano Solo(Piano Version by Composer)

There are 7 opus numbers, i.e. 5, 6, 8, 10, 11, 72 and 98, with “a” and “b” appended, hence the total number of music pieces is 14.

What does “a” and “b” mean? It certainly is not the timeline since for opuses 5, 8, 10, 11 and 72, a and b were not appended in the order in which they were composed, although for opus 6, they were. As for opus 98, we do not know which was composed first. It is the same for publication year.

As for the musical quality of the pieces, it is not possible to determine. I personally think pieces with “a” are superior that those with “b”, but this is merely a personal opinion.

Number of pages could be the answer. If we compare the number of pages (if they are in multiple parts, we calculated the total), “a” pieces are larger than “b” pieces.

This issue was discussed by Dr. Busk and myself while compiling 「Piano Sonata Pieces」. Dr. Busk believes that they are in the order of the composed year, which is common sense in the musicology.

In 「Piano Sonata Pieces」scheduled to be published this fall, there are 4 pieces with alphabets appended. These are 5a, 6a, 6band 8a. Dr. Busk agreed to using 6a and 6b as opus number but was against 5a and 8a. But I was able to convince him and Dan Fog numbers are used in the publication. My reasoning was that Dan Fog numbers are already used and referenced in many publications and changing them would cause confusion.

Based on study, Mozart’s Koechel numbers have also gone through some changes over the years. As study on Kuhlau proceeds, there may be a time in which we should review these opus numbers. Studies have already discovered many changes necessary in the composition years in Dan Fog’s catalog. Dr. Busk is already advising Mrs Lene, successor of Dan Fog, that corrections should be made when reprinting "Thematic-bibliographic Catalog" .

There are still many question marks in the study of Kuhlau. It is my hope that young researcher will come forward to continue with this study.

Toshinori Ishihara (04/23/2012)
(Translated: Kyoko Ueno)