Warning: this post will be discussing face-melting guitar solos, so please don’t read any further unless you are OK with the melting of your face. Heed your potential future forecasted in the album cover below:

I have to admit that I was recently jamming along with Deep Purple’s “Smoke on the Water” (from their album Machine Head). I probably haven’t jammed along to that song since I was 15, so my memory of the song was a little faded. On casual listening, I always assumed the form of “Smoke on the Water” to be basically a pair of verse/chorus parts, followed by a solo over the verse/chorus part, with a final verse/chorus and riffs inserted in the middle. In other words:

Riff
Verse/Chorus (1)
Riff
Verse/Chorus (2)
Riff
Verse/Chorus (solo)
Riff
Verse/Chorus (3)
Riff

I didn’t really think there was much if any difference between the verses and choruses throughout the song. But when I began playing along with the solo section, I noticed that the harmonies were not the same as they had been in the original verses and choruses. Take a listen to the opening vocal parts from the song:

		Deep Purple: “Smoke on the Water” (verse)
		Deep Purple: “Smoke on the Water” (chorus)

The table below shows a basic analysis of the chord changes in both the verse and the chorus during the vocal parts (FYI, the second time through the chorus, it gets elided into the riff):

Verse:
I	I	I–bVII–	I
Chorus:
IV	bII	I	I

Now listen carefully to the chord changes underneath the solo section:

		Deep Purple: “Smoke on the Water” (solo, first part)
		Deep Purple: “Smoke on the Water” (solo, second part)

You should hear that, although the harmonies sound similar, they are not exactly the same while the guitar is soloing as when the singing is happening. Here’s how I hear the basic pattern of chord changes through the solo:

Solo (verse-like):
I	I	IV	I
Solo (chorus-like):
IV	IV	bVII	bVII

As you can see and hopefully hear, the solo section has a lot of similarities to the original verse and chorus but also is more of a variation than an exact copy. In many other songs, solos often happen over exact copies of the verse and/or chorus harmonies. Since the solo section in “Smoke on the Water” has been reharmonized, however, I think we should probably call it a bridge. Bridges typically happen after a pair of verse/chorus sections to add variety in the song. In fact, just having the break from singing to soloing is probably enough variety to call maybe all instrumental breaks “bridges” on some level. With “Smoke on the Water,” I think we can see a good example of songwriters moving away from merely pasting a solo over previous material for contrast and instead developing the contrasting material to be even more effective.

Thanks to John Covach, I can provide another example of a song whose guitar solo further extends the function of a contrasting bridge section yet is still tied to the verse/chorus core. The song in question is “More Than a Feeling” by Boston off their self-titled album. This example is a little more complicated since the verse and chorus are in different keys, but hopefully it will be clear. Here are the audio clips for the basic sections:

		Boston: “More Than a Feeling” (verse)
		Boston: “More Than a Feeling” (chorus)
		Boston: “More Than a Feeling” (solo)

I’ve written out the harmonies for each of the parts of “More Than a Feeling” in the table below. Realize that the verse begins in D major, the chorus begins in G major, and the solo is solidly in D major.

Verse:
D major:	I	bVII–IV6	I	bVII–IV6
Chorus (main part):
G major:	I	IV	vi	V
Chorus (end transition):
D major:	ii	V	IV	IV
Solo (first part):
D major:	I	IV	I6 or vi	V
Solo (end part):
D major:	I–vi–	ii–V–	IV	IV

Now my little 4×4 table doesn’t do justice to the interesting phrase lengths in the song, but I’ve tried to boil it down to something that you can easily compare. It’s easier to match up the table if you play along with the song (because of the modulations), but I think you can get the gist by using your ear. As you can see, the first half of the solo is basically the chord changes from the main part of the chorus; the harmonies are transposed from G major to D major and the I⁶ is put in as a subsitute for the submediant (vi), but it’s basically the same. The second half of the chorus, which affects the modulation back to the verse in D major, is a little squished in the second half of the solo because the modulation doesn’t need to happen, but by the end of the solo, the relationship to the end of the chorus should be clear. To summarize, though, I think you can see how in “More Than a Feeling,” one part of the song (the chorus) is organically developed into another part (the solo) to create a contrasting bridge that still ties into the song as a whole.

Let me provide one final example, which is the simplest and most clear case of a solo as bridge. Take a listen to the three basic parts of AC/DC’s “Dirty Deeds Done Dirt Cheap” off the album of the same name:

	AC/DC: “Dirty Deeds Done Dirt Cheap” (verse)
	AC/DC: “Dirty Deeds Done Dirt Cheap” (chorus)
	AC/DC: “Dirty Deeds Done Dirt Cheap” (solo)

As you should be able to pretty clearly hear, the verse is rooted strongly in the tonic (I). The chorus, as a foil, begins on the subdominant (IV) and then moves back to tonic. After the standard pair of verses and choruses, the solo then comes in over a strong dominant (V). This dominant chord is the first one that has occured in the entire song. Even the opening riff only touches on I, bIII, IV, and bVII; every member of the pentatonic scale is there except for V. So when the solo (as bridge) occurs, it’s almost as if the final piece of the puzzle is added. In this case, the solo/bridge doesn’t develop a previous part of the song; rather, it organically extends the tonal motion of the verse and chorus sections. The whole song is almost like one big expansion of a twelve-bar blues.

In summary, I’d like to point out that in each of my musical selections, the solo has followed two iterations of verses and choruses. In this place in the form, the solo can be seen as acting as a bridge, especially since the solo is followed by the third and final verse/chorus part in each song as well. What is interesting in these examples is how the instrumental solo has taken on more of a bridge-like quality through either varying the harmonic changes (via substitution, transposition, compression, etc.) or adding a new harmonic area (as is perhaps more typical of bridges). Thus, when thinking about how and where that solo should go in your next song, maybe consider giving the solo its own special part. I mean, it’s got to be pretty darn special if it’s going to melt your face.