The items BWV 439–507 in the catalog of works of Johann Sebastian Bach are songs that appear in Schemellis Musicalisches Gesang-Buch.

The 69 scores are ordered alphabetically according to their title without distinguishing the letters I and J. For each song, the title is identical to the first few words of the lyrics.

Each song has two voices:

• a soprano voice with lyrics, and
• an accompanying bass voice typically with figured bass.

We quote an article on Georg Christian Schemelli [1] regarding the collection of songs:

Of a decidedly Pietistic bent, [Schemellis Musicalisches Gesang-Buch] contains

• the texts of 954 hymns, and includes
• engraved plates giving melody, figured bass, and first verse or text incipit for 69 of these.

J.S. Bach seems to have acted as musical consultant for the project. In the preface the compiler states that the tunes in his book were partly newly composed, partly improved, by J.S. Bach. This is borne out by the presence of J.S. Bach's hand in the reproduction engravings from the collection, either throughout a given setting, in the bass only, or in isolated passages in the bass.

Despite being listed in the Bach-Werke-Verzeichnis, the authorship is unclear for some songs. The article states:

Various authorities on the life of J.S. Bach have spent much labour in investigating which were the tunes newly composed by him, and which were merely revised and corrected by him.

• While Spitta attributes 29 out of the 69 tunes to J.S. Bach,
• Franz Wüllner, the editor of the volume of the J.S. Bach Gesellschaft (xxxix.) in which the hymns appear, considers that only 24 are J.S. Bach's;
• while Q.-L. assigns only 22 to J.S. Bach.

According to recent research, only three melodies from the collection have been attributed to J.S. Bach:

• Dir, dir, Jehova (autograph in Anna Magdalena's Music Book of 1725), BWV 452;
• Komm, süsser Tod (attributed to J.S. Bach on stylistic grounds), BWV 478; and the beautiful
• Vergiss mein nicht, BWV 505.

The last, curiously enough, is the only one of the sacred songs of which the collection mainly consists, to which J.S. Bach name is appended to (above which is written 'di J.S. Bach, D.M. Lips'.).

Objective

We provide transcriptions/harmonizations of each song for four voices. Specifically, two voices are added in between the original soprano and bass voice.

Below, the concept is illustrated at the first few measures of Mein Jesu, was für Seelenweh, BWV 487:

Input: Original score with 2 voices

⇓
Output: Score with 4 voices

Our goal is to achieve the compositions as faithfully as possible to the style of J.S. Bach.

Method

We employ a fairly recent approach: Data-driven music composition as custom implemented by our The Pirate Fugues software.

At this point, we kindly suggest to the reader to have a look at one, or two example transcriptions: please, click any number in the menu and watch the video animation ... and only then continue reading the description below.

The Pirate Fugues software has a unique combination of features:

• includes a database of approx. 4300 classical scores;
• calculates note suggestions for gaps in the score deterministically;
• displays and allows user to filter the suggestions.

The capabilities allow for a variety of compositional tasks. In the following, we describe the application in the context of our particular challenge, namely to create transcriptions for the songs from Schemellis Gesangbuch:

Two of four voices are already fixed. Initially, the two newly introduced voices are blank. The software computes suggestions for these gaps based on

• the subset of 1783 scores in the database attributed to J.S. Bach, as well as
• algorithmic criteria to enforce similarity to these scores.

Typically, the suggestions on how to fill the two empty voices with notes

• cover a range of 1–3 measures, and
• range from 10–30000 in quantity.

At this point, the user takes over: Upon inspecting and filtering the suggestions, the user makes a subjective choice and finalizes the notes.

Consistency

There are three deterministic criteria to measure the consistency of the resulting piece to the scores in the database.

In the video animations, the numbers in three top rows indicate the frequency of a musical transition in the scores of the database selection. The number 0 represents no occurrence for a particular criteria. The ratio of non-zero ratings is tabulated for each transcription and criteria in the Contents section.

The performance of the software varies from piece to piece and from measure to measure. Despite a large database selection, and relaxed criteria, the following undesirable scenarios might occur:

• no suggestions are available due to the initial conditions;
• the suggestions are unpleasant, or not suitable for the specific location in the score

Then, the user reverts to the conventional, full-manual mode of composition.

Omissions

Our approach disregards the figured bass. This decision can be considered as controversial, since the figured bass is assumed to be of Bach's own writing.

Any fermata on a rest is waived, because the notation is not supported by our software.

The song Gib dich zufrieden und sei stille, BWV 460 appears in three variations. We only treat the 3rd version and do not cover the others. Therefore, our production does not include

• Gib dich zufrieden und sei stille, BWV 460a
• Gib dich zufrieden und sei stille, BWV 460b