Sort bibliography with same author and same year (biblatex)

Question

When I cite two works by an author published in the same year, biblatex will sort them in the bibliography according to their title. In some cases, however, I know that the work sorted in the second place in fact was published first. How can I reorder them?

\documentclass{article}
\usepackage{filecontents}
\usepackage[style=authoryear,sorting=nyt]{biblatex}
\begin{filecontents}{\jobname.bib}
@BOOK{lennon1972a,
    AUTHOR = "John Lennon",
    TITLE = "My music",
    YEAR = "1972"}
@BOOK{lennon1972b,
    AUTHOR = "John Lennon",
    TITLE = "More of my music",
    YEAR = "1972"}
\end{filecontents}
\addbibresource{\jobname.bib}
\begin{document}
\cites{lennon1972a}{lennon1972b}
\printbibliography
\end{document}

Answer 1

Inspired by henrique's answer, the best way seems to use the sorttitle option, as explained in §3.5 of the biblatex documentation. According to that description, biblatex sorts in this order:

1. presort 2. sortkey 3. author 4. year 5. sorttitle, if defined, otherwise title.

No. 1 and 2 are normally left undefined. To override the sorting by title in 5, define sorttitle:

\documentclass{article}
\usepackage{filecontents}
\usepackage[style=authoryear,sorting=nyt]{biblatex}
\begin{filecontents}{\jobname.bib}
@BOOK{lennon1972a,
    AUTHOR = "John Lennon",
    TITLE = "My music",
    YEAR = "1972",
    SORTTITLE = "a"}
@BOOK{lennon1972b,
    AUTHOR = "John Lennon",
    TITLE = "More of my music",
    YEAR = "1972",
    SORTTITLE = "b"}
\end{filecontents}
\addbibresource{\jobname.bib}
\begin{document}
\cites{lennon1972a}{lennon1972b}
\printbibliography
\end{document}

Answer 2

See the sorting option in the biblatex manual. The default is, as you say "nty" (Name, then Title, then Year) but this can be changed or you can define your own custom sorting scheme (See \DeclareSortingScheme). It looks like you probably want sorting=nyt.

Alternatively, you probably want to make your .bib know which one came first (there's not much point in just you knowing ...). Put in a MONTH field in your .bib to distinguish the entries within the same YEAR and then use a custom sorting spec:

\DeclareSortingScheme{nymt}{
  \sort{
    \field{presort}
  }
  \sort[final]{
    \field{sortkey}
  }
  \sort{
    \field{sortname}
    \field{author}
    \field{editor}
    \field{translator}
    \field{sorttitle}
    \field{title}
  }
  \sort{
    \field{sortyear}
    \field{year}
  }
  \sort{
    \field{month}
  }
  \sort{
    \field{sorttitle}
    \field{title}
  }
  \sort{
    \field[padside=left,padwidth=4,padchar=0]{volume}
    \literal{0000}
  }
}

Then use the option sorting=nymt

If you don't want to see the months in the bibliography, put this in your preamble too:

\AtEveryBibitem{\clearfield{month}\clearfield{labelmonth}}

Answer 3

What you're looking for is something like the sortkey field (or perhapspresort). Check §3.5 (or §4.5.5 for more complicated sorting schemes — check this answer for a good example) of biblatex documentation

IMHO, you should consider a bibliography as an index for citations; it's meant to "decode" the citation labels, and to offer the reader a good compilation of literature on the subject. However bizarre it may seem, changing the sorting scheme halfway could make your bibliography confuse.

Here's a MWE:

\documentclass{article}
\usepackage{filecontents}
\usepackage[style=authoryear,sorting=nyt]{biblatex}
\begin{filecontents}{\jobname.bib}
@BOOK{lennon1972a,
    AUTHOR = "John Lennon",
    TITLE = "My music",
    YEAR = "1972",
    SORTKEY = {a}
  }
@BOOK{lennon1972b,
    AUTHOR = "John Lennon",
    TITLE = "More of my music",
    YEAR = "1972",
    SORTKEY = {b}
  }
\end{filecontents}
\addbibresource{\jobname.bib}
\begin{document}
\cites{lennon1972a}{lennon1972b}
\printbibliography
\end{document}

Answer 4

The easiest way, is to set up the month in your bibliography file as it is the default fallback for ordering, like:

month = jan

(In case of a prolific author you can also aim for the day of the publication)

If you don't know it, and don't want to put an artificial one, or if you want another solution, you can also edit your .bbl file after the compilation, to manually reorder the two articles (And change their name) and compile again. From:

 \bibitem[Lennon 1972a]{lennon1972b}
John Lennon.
\newblock More of my music. 1972

 \bibitem[Lennon 1972b]{lennon1972a}
 John Lennon.
 \newblock My music. 1972

to

 \bibitem[Lennon 1972a]{lennon1972a}
 John Lennon.
 \newblock My music. 1972

\bibitem[Lennon 1972b]{lennon1972b}
John Lennon.
\newblock More of my music. 1972

(As long as the number of conflicting paper in this case is small, this solution can be effective)