For most of the run of the conventional sheet music that people play, reading the key signature will tell you what key you are in--although this is only true because it is the convention to write it and name it that way--passing key changes are reflected by using accidentals rather than by a change in the key signature--As is typical of mudcat music discussions, this one is not specific about what sort of music is being discussed, so any "rules" can be blown out of the water with an example from any kind of music in the world that doesn't follow those rules---
Pavane's point about modes is either irrelevant or quite important--depending on what sort of music you are dealing with--those of us who have studied formal music theory know that technically, modal music came before keys were introduced, so that they are different animals--how and why they are different is a fearful path that it is better for everyone but composers and people who write music software to avoid--
Foe, Pavane was, perhaps a little unfair to you, since the scale you did manage to find is the natural minor--but classical composers tended to use a melodic minor scale which had different intervals ascending and descending--and he probably felt that since you didn't know this, it was probably a little early for you to begin giving lessons in music theory--
And, Master Pavane, will those of us with Mac's ever be able to try any of your most interesting programs?