For example, you take an A major scale, you start on the second note (B) and go up to B, you have Bm dorian mode; you start on the third note (C#) and go up thru the scale to the C# an octave above, and you have C# phrygian, etc etc. That's how you can *construct* modes.

But that's not neccessarily how you *use* them.

For example, you can play those seven notes (B C# D E F# G# A) all day long until the cows come home, but if the underlying chord or tonality is A, what you're playing is not going to sound like anything other then A major, no matter what note you start on, or what notes you try to emphasize.

But switch the underlying chords or tonality to Bm, or use them in a song that's in the key of Bm, and voila: it now sounds like B dorian.

Its the underlying chords and tonality that determine what mode any seven notes (i.e. a scale) sounds like. Not starting or ending on any particular note.