Learning about modal sounds requires an understanding of standard musical scales. The C major scale is played without sharp or flat notes, the white keys on a piano from C to C. The mode that you hear in a normal major scale is called Ionian. The different church modes simply start on different tones of a scale with the accidentals, sharps and flats, kept the same as the parent scale. For example, a Dorian mode is played as D-E-F-G-A-B-C-D and the related Ionian C major is played as C-D-E-F-G-A-B-C.
Musical modes and scales have been developed over a span of centuries. It is nearly impossible to credit an individual or certain time period for the creation of an art form. Medieval churches used the modes to change the sound of their music and the overall effect. These scales have been codified as early as the eighth century and used ever since.
The modal naming system was inspired by Greek names in the ninth century. The same names used today were mentioned in Greek writings, but connecting the name with the actual scale may not be exact. The names of the scales in order, starting with the first tone and moving to the seventh tone are: Ionian, Dorian, Phrygian, Lydian, Mixolydian, Aeolian and Locrian.
When you hear music, there is an expectation that the musical phrase will end in a certain way. A perfect cadence, in the Ionian mode, is a standard way to end a tonal piece of music and is what you commonly expect to happen. In the modal system, the way a phrase is ended depends on the next step that is going to be taken. A leading voice is usually used to end the first phrase and set up the next section. This is a major difference in the way modal music changes with the specific mode.