I an amateur pianist and I have theory knowledge. I know what a chord progression is. Although I mostly read from score I can easily listen a music and reproduce it on the piano. People often ask me for the chords, but recently I was asked the chord progression for the music. What do they expect?
A chord progression is a series of chords that are played in a song (or a part of the song).
If a song has the chords C, Em, F, G, It means that all these chords together form the chord progression of the song. Many people abbreviate 'chord progression' to 'chords'. It's the same thing. You might also hear harmonic progression and/or chord changes (or simply 'the changes').
Someone might ask you for the chords or the chord progression, but basically he's asking for the chord progression.
Actually, "chord progression" connotes a different level of abstraction than simply "chords". For each chord in a particular key, let's say the key of C: C major would be the "I" chord. D major would be the "II" chord, etc., up to B major which would be the "VII" chord. Of course, major chords are composed of minor thirds on top of major thirds. Minor chords are composed of major thirds on top of minor third intervals and hence, minor chords are noted as lower case roman numerals: i, ii, iii, etc. The PURPOSE of such a notation is to allow you to transpose this relationship among chords from one particular key to any of the eleven others. Now, "chord progression" is then the RELATIONSHIP among the chords that then define the harmonic construction of the song. So, "I, IV, V, I" would be an example of a chord progression. Read any decent music theory book and all this should be covered. cheers, Paul.
All the answers so far are correct but I would like to see if I can explain it in a different way that might make it easier for some folks to understand.
Every song has a basic harmonic structure to go with the melody of the song. The chords provide the harmony and appear in a predictable predetermined order. So the chord progression of a song is not only a list of all the chords, but the order they are played.
The chord progression of the verses of a song are often different from the chord progression for the chorus or bridge. But the chord progression for the verses will repeat for each verse - same with chorus.
There are common progressions that appear in many songs because the follow a logical order of ascending harmony and returning back to home base.
A chord progression can be identified by naming the exact chords such as "G - D - Em - C" or you can identify a chord progression by the chord degree based on the root key. So that in the key of G major - G D Em C becomes "I - V - vi - IV" (capital Roman Numerals indicate Major and lower case indicate minor). By translating the chord progression into the numeric representation, an accomplished musician should be able to play the song in any key.
They just want to know how the harmony of a song progresses though the chords of a song. The chord progression can just be viewed as the precises order of the chords in a song. The chords used and the order appear in offer a lot of information about the song and how they can play it.
For example off the top of my head I know the chord progression for Let It Be by the Beatles which is
C G Am F C G F C. The song itself only uses four chord which are C, G, Am, and F, but the order of the chords and how they progress is important to the song and how it feels. Especially since this song is unique by using a IV-I cadence instead of the typical V-I cadence.
Using the progression, I can voice the chords in a way that makes sense for the progression, figure out the key which is C major in this case, figure out what scales and modes make most sense to use at this part of the progression, and even reduce the progression to its Roman Numeral analysis using the chord progression to not only analyse the harmonic movement of the progression, but easily be able to transpose it to any key.
Chord progressions are written with a sequence of letters representing the chord along with its attributes such as minor, suspended, or diminished. (Note: All chords are assumed to be major unless otherwise indicated.)
An example would be C,G7, Am, F with the assumption that it would be repeated. Typically the bass line defines what your progression will be. This is particularly true for piano. So they basically want to know what "progression" is guiding the music. Also keep in mind that the measure count is also important. It may be 1 measure of each chord that repeats or it may be 2, or even a half a measure here and there. But basically the notation they'll expect is simply a sequence of letters with minor as a lowercase "m", suspended as "sus" and so on.
In the key of C Major using 7th chords as in jazz, the chords are C Major 7, D minor 7, E minor 7, F Major 7, G7, A minor 7, and B minor 7 flat 5. Count starting with C Major, 1,2,3,4,5,6,7. So in answer to your question, What would a ii, V, I be? Answer is D minor 7 (the ii), G7 (the V) and C Major 7 (the one). Other common chord progressions in jazz are I, vi, ii, V ; iii, vi, ii, V. If you look at your music, you will see the ii, V,I or other progressions in the song. A progression such as ii, V, I, is always a ii, V, I, no matter what key you play in, so musicians communicate in the language of chord progressions.