Cecilia Bartoli could have followed the path of least resistance. When the Italian mezzo-soprano burst onto the opera scene in the early '90s with a standard repertoire of Rossini and Mozart, she looked like she could establish a career as a traditional classical artist.

Her 1992 album, If You Love Me, has sold 190,000 copies, according to Nielsen SoundScan; a later effort, the 1999 Vivaldi Album, sold 75,000 copies.

It would have been easy for her to simply release more mainstream efforts and watch the money roll in. But as her fame grew, so did her appetite for more adventurous work. And while none of her more recent albums have sold as many copies as her earlier projects, Bartoli says she's grateful to have the opportunity to bring lesser-known music to light.

Her 2005 album, Opera Proibita, unearthed music that was outlawed in 18th-century Rome because of papal censorship, while the 2006 Maria explored the work of early-19th-century singer Maria Malibran and featured eight world-premiere recordings.

Bartoli's latest research project/release, out October 27, is Sacrificium (Decca), a deep dive into the cruel world of the castrati -- 18th-century male singers castrated as boys to maintain the high tones of their voices.

I have always sung a lot of music which Mozart wrote for the castrati, Bartoli says. But when I devoted a project (Opera Proibita) to my hometown, Rome, I for the first time read more about the strange and sad facts that lie beneath the castrati phenomenon. I noticed that many people know music that was written for castratos, but do not know about the tragedy behind it. I think it is most important to talk about this, because it deepens our understanding for this music and it helps me as an interpreter.

In addition to the music, the two-CD set includes a hardback book and a 152-page booklet that includes a libretto and the Castrato Compendium, an A-Z guide to the era assembled by Bartoli that also features an essay she wrote.

It's a heavy undertaking for an artist and a label, but Decca is steadfast in its support. Cecilia Bartoli is not a typical classical artist, nor does she create typical classical releases, marketing manager Joseph Oerke says. With her, more than any other artist, the customer gets not only the music but also a completely researched project and supplemental materials. Though we recognize that this is a trying time for the industry, such is the name Bartoli has built for herself, the quality of her work and Decca's unwavering confidence in her that we believe this packaging to be not only deluxe but essential to the project.