Before they went to composition software, composers used to scribble notes on music manuscript paper.

If a few famous portraits of the masters can be believed, they often strolled about clutching works in progress.

These days, those who keep the music of composers alive seem to have the same relationship to calendars.

Anniversaries - whether birth or death-years, round-numbered or in multiples of 25 — have entered the classical-music mainstream as a marketing tool, a creative energizer and a way to focus the public’s attention. They’ve even begun to include world events, performers and teachers of note.

Indianapolis is having its share of such anniversaries this year.

Last month, the Indianapolis Symphony Orchestra wished a happy 200th birthday to Felix Mendelssohn.

This month, classical music fans can celebrate the 20th anniversary of the fall of the Berlin Wall and the 100th birthday of Indiana University professor and violinist Josef Gingold, who died in 1995.

“Thematic concerts create a marketable package,” said Jessica Di Santo, director of communications at the ISO. “You can put together themes you wouldn’t do without (the anniversaries). It can help you be more creative than you would be otherwise.”

The ISO will add to the international celebration of Gustav Mahler’s birth sesquicentennial next spring with performances of the “Resurrection” Symphony, which Butler University will present next weekend.

Butler’s Richard Auldon Clark said that on college campuses, anniversaries can help foster interdisciplinary work.

“We can find one central figure and open it up to the whole college community,” he said.

That’s the case with the Mahler Project that’s running throughout Butler’s school year. Besides concerts, it includes a lecture, a poetry reading, classic film showings and dance performances.

“There were his struggles as an artist, but also the anti-Semitism of Austria in the late 19th century and Mahler having to convert to Christianity,” Clark said.

“You open the door to art history and the artists of that time and their political struggles. It just spiraled from there. You can open the door to every kind of academic pursuit. Mahler was just the springboard for this huge festival.”