Popular songs that include modulation?

Modulation is not simply changing keys but changing gradually from one key to another, often through chords that are ambiguous, and establishing the new key through chords that are not ambiguous. The Beach Boys song "I get around" mentioned by conoehead is very interesting harmonically but doesn't contain anything Mozart would have recognized as modulation. The key changes in the second verse suddenly, *without* gradual transition. To the classical ear this would have sounded barbaric. (See the chords http://tabs.ultimate-guitar.com/b/beach_boys/i_get_around_crd.htm.) The chords in the verse by itself would also have sounded barbaric, as not really belonging to one key at all. In general I think it's harder to find real modulation in pop songs because we have a much more open sense of tonality than classical era composers. So where they felt a change of key was something that had to be approached with care or slight-of-hand, and had a clear sense of when a passage was unmistakably in one key or another -- as opposed to being transitional, without an abiding key center -- we are more forgiving and less demanding. To understand modulation it might help to listen to some classical music. In the http://en.wikipedia.org/wiki/Sonata_form, which was used for the first movements of symphonies, string quartets, and the like, there were prototypically two sections called the first subject and the second subject. At the beginning of the piece, called the exposition, there was a transition section between the first and second subject that modulated clearly from the main key of the whole piece that was used for the first subject, to another key, usually V, used for the second subject. However, at the end of the movement, the first subject is succeeded by the second subject without modulation, so they are both in the same key. Usually the original transition between the two is recalled, but without actually modulating. In the middle of the piece was the development section, where there was typically lots of modulation between various shorter sections with less sustained key center. Listen, maybe to https://www.youtube.com/watch?v=nLcY0gqbN3I. (Chosen kind of randomly.) 1:04 is the beginning of the second subject the first time through, 6:04, the second subject reappearing at the end of the piece. First time there has been a modulating transition; at the end, a transition without modulation. Somewhat easier to hear is a modulation from 1:11 - 1:19 (from G to Eb) followed by a quick modulation back (to G) at around 1:32. You can check out the score to see exactly what's going on http://imslp.org/wiki/String_Quartets,_Op.76_%28Haydn,_Joseph%29. (The pop song that did first occur to me as having something modulation-like was Elvis Costello's https://www.youtube.com/watch?v=Ow1S4DJtLOk. The final verse is a whole tone higher than the first verse, the verse key center is pretty clear, and the bridge, from 1:34 to 1:53, prepares it in a clear way, without having a super-clear key itself, and so is kind of modulatory. But I suspect Mozart would have raised his eyebrows here, too, 'cause the bridge starts rather abruptly itself. Yet it's interesting that in Oliver's Army, unlike the Beach Boys song, the raising of the final verse is not super obvious to the ear, due to the abruptness of the shift being displaced into the transitional bridge, where, in the pop style, harmonic adventurousness is more expected. Chords http://tabs.ultimate-guitar.com/e/elvis_costello/olivers_army_crd.htm.)

The Da Vinci's Notebook song https://www.youtube.com/watch?v=734wnHnnNR4 not only has an example of modulation (at 3:33), but also explicitly calls it out in the lyrics. It's the reason I know what modulation is.

Two pop songs: Beach Boys "I get around" Roger Miller "chug a lug"

Bob Wills, "New San Antonio Rose," modulates to V on the bridge. Country and R&B duets (male/female) also tend to have sophisticated modulations between the gender-specific verses to accommodate the ranges of both singers. A good example is George Jones and Tammy Wynette, "Golden Ring,"

Additionally, modulation upwards by a semitone or a step is commonly used in country for emotional intensification. Examples are the half step rise on the last verse and refrain of George Strait's "Amarillo By Morning," or the last chorus of Patsy Cline's "Walking After Midnight," to name two of hundreds of examples.

Bertran, that is incredibly helpful and straightforward. Your explanation is the one I'm most familiar with, but in my jazz studies a (rare but reoccurring) joke is "bro, do you even modulate?" I'm very familiar with shifting up a whole or semitone, but, while technically modulation, it seems too "easy". Kinda gimmicky, but I prefer your "barbaric". I love love love the idea of starting in one key, playing a transitional bridge with ambiguous chords and resolving to another key with unambiguous chords. I'm going to play around with that, thank you so much for the Costello inspiration. On a lark I recently watched the whole http://en.m.wikipedia.org/wiki/The_Unanswered_Question_(lecture_series) on pentatonics and musical phonology. Modulating to a IV or V seems natural, that Haydn went from G to Eb (sharp V? Flat vi?) without me really noticing is gorgeous.