Previously I mentioned Harmonic Movement as a way to create tension, building interest in music. Then I thought I probably ought to talk about Harmonic Movement and its roll in Contemporary Classical Music and to do that start with a brief history of harmonic movement.
When music began to move into more complex harmonies than the single or duet lines of Gregorian Chant, it did so by harmonising notes that sounded pleasing, but music was more horizontal in terms of movement of each line, rather than the vertical harmonies created by multiple lines. By the time of the Renaissance, chord progresses still weren't a developed concept. Multiple voice music was beginning to play with progressions, with the development of a ground bass. There where certain progressions music made more enjoyable (see Passamesso Moderno and Passamesso Antico), but cadences which provide a resolution to the harmonic movement were not common practice.
By the time of the Baroque composers, harmonic progression had establish a IV, V, I movement - that is to say, a chord IV (F-A-C) moves to a chord V (G-B-D) which resolves to a chord I (C-E-G). The I chord considered the tonic chord. The IV chord considered the Sub-Dominant and the V chord considered the Dominant. Adding a 7th to the V chord made the movement to the I chord even more satisfying. Playing with the triads within the standard (Western) scale created a variety of different cadences, but the IV, V7, I was the standard end cadence. The reason the V7 felt the need to resolve to a I chord is due to the leading note - in the above example, the B. In the V7 chord we know we are not hearing a I chord, because in the Key of G the F would be sharp (G-B-D-F#). A V7 in the key of C is G-B-D-F, so this chord in obviously not in the root position of the key; this chord is considered unstable as a result. The B in this chord "wants" to move up. With the I chord, the B resolves to C and we feel as if we have reached a place of stability.
As composers experimented with chords, new additions to the progression were introduced. A V chord (G-B-D) in the key of C can also be a I chord in the key of G. The V chord in the key of G is D-F#-A. If you play this chord before a G chord it sounds as if you are going to resolve to a G chord (especially if you include the 7th, a B). Then, if you play a V7 in the key of C (G-B-D-F) the need to continue to resolve is still present and so a further movement to the C chord (chord I in the key of C) is necessary. This sort of movement provides composers with the ability to shift keys and adds interest to the final cadence by extending the cadence and the need for resolution. Romance composers extended this exploration of the triad by introducing Neapolitan 6th Chords which extended the sense of the leading note to more than just one note. Then stringing by these chords together, composers could create chains of chords resolving to chords which resolve to chords.
Moving into the 20th century, composers began substituting chords, using chords in place of similar chords. For example, the ii chord (D-F-A) is similar to the IV chord (F-A-C) Add the 7th to the ii chord and you have the same chord with the added D. This type of chord substitution is really popular in jazz, creating a II-V-I progression, a jazz standard. Other types of progressions where developed, each one indicative of a style of music, such as Ragtime Progression and Blues Progression. There are also a whole series of progressions when dealing with melodic minor modes - and worthy of a book on the topic (let alone a brief blog).
Ultimately, the result is a host of different chord progressions that eventually lead to some form of resolution. The different progressions have different sounds, creating different feelings in the music, thus the reason Ragtime has a different progression from Blues and so on. Recently there has been resurgence in using modes (or scale) from before Baroque period and the established use of the tonic chord as the root of music progression. Twelve-tone music and serialism have a completely different concept in terms of harmonic progression - and, again, are really a whole topic on their own.
The concept of tension in Western tonal music is based on the desire to return to the tonic or chord I. As the music strays from this chord, the music builds tension. The tension is then released when the music returns to the tonic.