Richard

Here's a way that I've found helpful in differentiating the two nomenclatures.

1) If you are building your modal scales using the sharp and flat notes of a particular scale: eg C to C, D to D, E to E etc. using only the white keys of the C major scale, then it makes sense to refer to them as the Ionian _OF_ C, the Dorian _OF_ C, the Phyrgian _OF_ C. This seems to conform to the usage (or at least the meaning) of classically trained musicians.

2) The other method starts by naming the home tone or root of the scale or tune, and then the mode to indicate the pattern of whole and half steps. Thus a C scale with no sharps or flats would be a C major or C ionian scale. If it has one flat (B flat - the flatted seventh), then it would be C mixolydian, and so forth. This seems to make more sense for us trad types, since it conveys two vital pieces of information: the home tone and the harmonic structure.

For those of you who don't like to get too technical but know your basic key signatures, a quick way to spot a modal tune is to look for a disconnect between the home tone (usually the first and/or last note of the tune) and the key signature. So, if it looks like it's in C major (= aeolian, normally nothing), G major (normally one sharp - F#), D major (F# & C#) or A major (F#, C# and G#) but it seems to be missing the last sharp or has one too many flats (whether in the key sig or as accidentals), then it's a mixolydian tune. And if it looks like a minor tune, but it has one too many sharps then its a Dorian tune: A minor (= aeolian normally nothing), E minor (normally F#), B minor (normally F# & C#), F# minor (normally F#, C# and G#).

Are you hopelessly confused? Hope not...it's a fun game to play once you get the hang of it.