It is not currently possible to apply for jobs with a group which has a completely unspecified line-up.
As an online service, we must ensure that clients can judge the suitability of an artist for their event based upon the reviews and recordings they view on that group's profile. If the line-up of the group booked by a client does not match the line-up of the group whose recordings they have previously watched and whose reviews they have read, then that trust a client has in the service Encore provides breaks down.
What to do if you only perform with groups which have variable line-ups
There are exceptions: some successful groups on Encore receive work for jobs while offering variable line-ups (for example, a string quartet being booked as a string trio). In these instances, at least some continuity of group line-up has been retained from one job to the next to ensure that the client can make an informed judgement of their ability. In this example the string trio line-up is similar to the string quartet line-up, minus one performer.
If you have a group that has a variable line-up, we suggest you create a group page which showcases as closely as possible a typical performance from that group. Please note that group pages of this sort are less likely to be booked than groups who can guarantee a client the same line-up as displayed in their media.