This solution modifies the default template for the label. This requires biber rather than bibtex as the backend. This means that the compilation sequence needs to be altered, too:
pdflatex <filename>.tex
biber <filename>
pdflatex <filename>.tex
with possibly an additional
pdflatex <filename>.tex
It will work fine with latex rather than pdflatex - just biber is essential.
\documentclass[12pt,french]{report}
\usepackage{babel}% needed for french
\usepackage[utf8]{inputenc}% needed for sample bib entry
\usepackage{csquotes}% recommended in output (biblatex)
\MakeAutoQuote*{“}{”}
\usepackage[T1]{fontenc}
\usepackage[backend=biber, style=alphabetic]{biblatex}
\DeclareLabelalphaTemplate{% adjust the template for the label based on the default one - requires biber
\labelelement{%
\field[final]{shorthand}% if shorthand specified, use it
\field{label}% if label specified, use it
\field[strside=left]{labelname}% if not, use the labelname e.g. author
}
\labelelement{%
\literal{,}% add comma
}
\labelelement{%
\field[strwidth=2,strside=right]{year}% take the rightmost 2 numbers from the year
}
}
\usepackage{filecontents}
\begin{filecontents}{\jobname.bib}
@article{Cha65,
author = {Charles, Daniel},
year = {1965},
title = {Entr’acte: “Formal” or “Informal” Music?},
journaltitle = {The Musical Quarterly},
volume = {51},
number = {1},
pages = {144--165},
}
\end{filecontents}
\addbibresource{\jobname.bib}
\begin{document}
\nocite{*}
\printbibliography
\addcontentsline{toc}{chapter}{Bibliography}
\end{document}

Note that you should check your MWE compiles before posting it. Yours spewed errors which required me to modify it in order to get to the point where I could begin thinking about your question. Minimal is great and definitely what's needed - just make sure it isn't so minimal it doesn't work!
Too Many Names
The above code will cause havoc if your entries have too many authors (or, indeed, if they have names which are too long). The following code will use only the first name but it will append a + if there are other names in the entry. (This seems to be default.)
\documentclass[12pt,french]{report}
\usepackage{babel}% needed for french
\usepackage[utf8]{inputenc}% needed for sample bib entry
\usepackage{csquotes}% recommended in output (biblatex)
\MakeAutoQuote*{“}{”}
\usepackage[T1]{fontenc}
\usepackage[backend=biber, style=alphabetic]{biblatex}
\DeclareLabelalphaTemplate{% adjust the template for the label based on the default one - requires biber
\labelelement{%
\field[final]{shorthand}% if shorthand specified, use it
\field{label}% if label specified, use it
\field[names=1,strside=left]{labelname}% if not, use the labelname e.g. author
}
\labelelement{%
\literal{,}% add comma
}
\labelelement{%
\field[strwidth=2,strside=right]{year}% take the rightmost 2 numbers from the year
}
}
\usepackage{filecontents}
\begin{filecontents}{\jobname.bib}
@article{Cha65,
author = {Charles, Daniel},
year = {1965},
title = {Entr’acte: “Formal” or “Informal” Music?},
journaltitle = {The Musical Quarterly},
volume = {51},
number = {1},
pages = {144--165},
}
@article{Cha66,
author = {Charles, Daniel and Christmas, Father and Fairy, Tooth and Pan, Peter and Beanstalk, Jack},
year = {1966},
title = {Entr’acte: “Formal” or “Informal” Music?},
journaltitle = {The Musical Quarterly},
volume = {51},
number = {1},
pages = {144--165},
}
\end{filecontents}
\addbibresource{\jobname.bib}
\begin{document}
\nocite{*}
\printbibliography
\addcontentsline{toc}{chapter}{Bibliography}
\end{document}

If an individual author has a very long name, you have a couple of options. One is to truncate all names to some number of letters. (The standard label uses this method with 2 letters but you can specify a different number.) The following uses the first 8 characters of the first author's name:
\documentclass[12pt,french]{report}
\usepackage{babel}% needed for french
\usepackage[utf8]{inputenc}% needed for sample bib entry
\usepackage{csquotes}% recommended in output (biblatex)
\MakeAutoQuote*{“}{”}
\usepackage[T1]{fontenc}
\usepackage[backend=biber, style=alphabetic]{biblatex}
\DeclareLabelalphaTemplate{% adjust the template for the label based on the default one - requires biber
\labelelement{%
\field[final]{shorthand}% if shorthand specified, use it
\field{label}% if label specified, use it
\field[strwidth=8,names=1,strside=left]{labelname}% if not, use the labelname e.g. author - use the first 8 characters of the first author's name
}
\labelelement{%
\literal{,}% add comma
}
\labelelement{%
\field[strwidth=2,strside=right]{year}% take the rightmost 2 numbers from the year
}
}
\usepackage{filecontents}
\begin{filecontents}{\jobname.bib}
@article{Cha65,
author = {Charles, Daniel},
year = {1965},
title = {Entr’acte: “Formal” or “Informal” Music?},
journaltitle = {The Musical Quarterly},
volume = {51},
number = {1},
pages = {144--165},
}
@article{Cha66,
author = {Charles, Daniel and Christmas, Father and Fairy, Tooth and Pan, Peter and Beanstalk, Jack},
year = {1966},
title = {Entr’acte: “Formal” or “Informal” Music?},
journaltitle = {The Musical Quarterly},
volume = {51},
number = {1},
pages = {144--165},
}
@article{Cha67,
author = {CharlesChristmasFairtyPanBeanstalk, Daniel and Christmas, Father and Fairy, Tooth and Pan, Peter and Beanstalk, Jack},
year = {1967},
title = {Entr’acte: “Formal” or “Informal” Music?},
journaltitle = {The Musical Quarterly},
volume = {51},
number = {1},
pages = {144--165},
}
\end{filecontents}
\addbibresource{\jobname.bib}
\begin{document}
\nocite{*}
\printbibliography
\addcontentsline{toc}{chapter}{Bibliography}
\end{document}

The other option is to override the default labelling for specific entries:
\documentclass[12pt,french]{report}
\usepackage{babel}% needed for french
\usepackage[utf8]{inputenc}% needed for sample bib entry
\usepackage{csquotes}% recommended in output (biblatex)
\MakeAutoQuote*{“}{”}
\usepackage[T1]{fontenc}
\usepackage[backend=biber, style=alphabetic]{biblatex}
\DeclareLabelalphaTemplate{% adjust the template for the label based on the default one - requires biber
\labelelement{%
\field[final]{shorthand}% if shorthand specified, use it
\field{label}% if label specified, use it
\field[names=1,strside=left]{labelname}% if not, use the labelname e.g. author - use the first 8 characters of the first author's name
}
\labelelement{%
\literal{,}% add comma
}
\labelelement{%
\field[strwidth=2,strside=right]{year}% take the rightmost 2 numbers from the year
}
}
\usepackage{filecontents}
\begin{filecontents}{\jobname.bib}
@article{Cha65,
author = {Charles, Daniel},
year = {1965},
title = {Entr’acte: “Formal” or “Informal” Music?},
journaltitle = {The Musical Quarterly},
volume = {51},
number = {1},
pages = {144--165},
}
@article{Cha66,
author = {Charles, Daniel and Christmas, Father and Fairy, Tooth and Pan, Peter and Beanstalk, Jack},
year = {1966},
title = {Entr’acte: “Formal” or “Informal” Music?},
journaltitle = {The Musical Quarterly},
volume = {51},
number = {1},
pages = {144--165},
}
@article{Cha67,
label = {CharlesCh},
author = {CharlesChristmasFairtyPanBeanstalk, Daniel and Christmas, Father and Fairy, Tooth and Pan, Peter and Beanstalk, Jack},
year = {1967},
title = {Entr’acte: “Formal” or “Informal” Music?},
journaltitle = {The Musical Quarterly},
volume = {51},
number = {1},
pages = {144--165},
}
\end{filecontents}
\addbibresource{\jobname.bib}
\begin{document}
\nocite{*}
\printbibliography
\addcontentsline{toc}{chapter}{Bibliography}
\end{document}

\begin{document}... \end{document}and which demonstrates the issue. A complete Minimal Working Example is much more useful than mere fragments. Could you also explain the problem? Is it that you are missing a comma and space? – cfr Apr 11 '14 at 23:42biberan option? – cfr Apr 11 '14 at 23:49