I find that I am still interested in the subject discussed in my previous blog entry. I can only speak from the perspective I know, which is the German system vs the American system.
In Germany a singer has a house with which they are affiliated. If she is sufficiently valued by the agents and with her house's permission, a singer will occasionally contract for roles elsewhere. The houses fill as many roles as possible with the singers contracted to them. The most efficient method is to double cast each role to account for emergencies. Both casts perform the roles--one is not understudy for the other. Unusual gifts such as the ability to sing Salome are filled from outside the ensemble. There are tiers of houses based on salary level and talent of the ensemble. Singing is an ordinary profession with regular hours and benefits, though holidays seem to be unknown.
Agents visit the lower tier houses to see performers at work and evaluate them for jobs in the better houses.
In America there are two tiers: stars and flunkies. I don't know how to put it more gracefully. Some people have ordinary jobs affiliated with the larger houses. San Francisco has the Adler Fellows. The Met has singers contracted to it. These people draw salaries, play minor parts, appear in community based concerts, give Schwabacher Debut recitals, and otherwise do nothing. They never play major roles in the main house. The major parts are all filled by people brought in from outside. At the Met under the management of Peter Gelb they don't even fill in in emergencies.
Appomattox used Adler Fellows in significant parts. This is unusual and can be explained by the fact that Appomattox is a modern opera.
Below the major houses in America is a rich layer of semiprofessional and amateur opera companies, none of whom have enough money to provide regular jobs for singers. Thus the division into
--stars--those who sing all the main parts in the professional companies and
--flunkies--people who sing major roles as amateurs and those who provide emergency backup for major houses.
How one crosses from flunky to star is one issue. I outlined my recommended path to success here. Joyce DiDonato seems to have found a way. Perhaps we should ask her.
On the whole either you are already established as a star, or an agent has to see you perform the role in question before you will be cast to sing a major role in a major house in America. That means getting jobs in places where the agents are looking. Elaine Alvarez made her way onto the main stage of the Chicago Lyric because Angela Gheorghiu skipped the rehearsals and Elaine could show off her skills.
The article about the future of opera is right about one thing: the German system produces the superior product. People benefit from working together on a sustained basis. Young singers improve much more rapidly when they are given real work to do. Germany today is the center of the opera world.