Lately I have been asked several times about how to be a more musical dancer, and how to “anticipate” what’s going on in a song to adapt your dancing to the music…
My obvious answer was (and is…) “listen to as much salsa music as you can”, but some people might not be satisfied with such a solution, and might need a more detailed explanation.

So, without further ado, here is a schematic chart of a typical song structure, some explanations, and an example using a contemporary piece…



Probably Four
One general principle which applies to most salsa songs of all genres is the “probably four” principle.
This term was coined by Don Baarns, a.k.a “the unlikely salsero”; visit his music4dancers series on youtube: http://www.youtube.com/user/Music4Dancers/videos
Especially this video: http://www.youtube.com/watch?v=_Lk5qBoeyz4
Most parts of a salsa song, although not in 100% of cases, are based on this rule; many elements take place during 4 or 8 clave cycles, which are, respectably, 8 or 16 bars of music.
When you notice a change, start counting out the bars: 1-2-3-4, 2-2-3-4, 3-2-3-4, 4-2-3-4, and by the last of them, something has probably changed again… this is due to the fact that salsa music is made in 4/4 timing, meaning that it is mostly structured around some pattern of 4 musical bars, or an n number of such “structures”, with n = 2, 4, or 8 in most cases.
Try it out yourselves!

Introduction
As you can see in the image above, most of songs have an introduction part; during this part of the song, the listener is introduced to the song, to the melody, to the whole “atmosphere” of the composition…
There is some percussive action going on during this part, as the intro often is a kind of a preview to the Montuno part of the song, which is the “main” part, when many of the interesting tricks the musicians have up their sleeves are revealed.

Cuerpo
After an ending note, many times a short percussion break, of the introduction comes the “Cuerpo” part of the song;
As the name suggests, this is the “body” of the song, which has most of the lyrics in it, using a structure of verses.
The verses are mainly performed by the main vocal, but sometimes also by the back vocals supporting it.
Most instruments play their typical pattern, accept the piano which may play the melody or some support notes;
Clave is sometimes played, the Conguero plays the 1 bar Tumbao, together with the Bass which plays its typical Tumbao based pattern;
The Bongocero plays the Martillo pattern on the Bongos, the Timbalero plays the typical basic cascara, the guiro sometimes plays its typical pattern as well as the Maraca shakers.

Mostly, no bells are played, and there might be some wind instruments supporting the orchestra as well.

Bridge
Between the “Cuerpo” and the “Montuno” sections of the song, there might often be a short “bridge” (puente) section, which is a sort of connection between the 2 main parts of the song. In Timba (Cuban salsa) this might be the 1st gear \ guia in the song;
During this part you might hear a repetition of one of the phrases of the Cuerpo, and some percussionists might change the patterns they play to more energetic and complex ones; there might be some improvisation involved as well, by both percussionists and vocalists, and sometimes even the piano \ keyboard and bass players;
might have some Coro-Pregon as well.
This is mostly a short section featuring 4, 8 or 16 musical bars in total.

Montuno
After the bridge, if such is present, starts the Montuno section of the song;
In many salsa songs, including most Timba compositions, this is the “main” part of the song, when most of the “action” takes place, all the tricks the musicians had kept under the table are revealed, there is much improvisation, and musicians show their true skills in action;
The rhythm holding instruments change – during the previous parts of the song, especially the Cuerpo, this roles was performed the the Conguero and Bass player, playing Tumbao (and Bass Tumbao, respectively), and sometimes the Clave;
Now, there are free to improvise, as the rhythm is now held by the Campanero, which is the Bongos player that now plays the Campana, using the more complex and syncopated pattern which exists for this instrument.
The Timbalero also moves up a notch in the “energy levels” of the song, now playing the Mambo Bell, also switching to the more dynamic “cascara mambo” from playing basic Cascara.
The main vocal, back vocals, and often some instruments (mainly percussion) engage in a typically Cuban “game” of African origin called “Coro-Pregon”, during which somebody “asks a question” (in the form of a note or a phrase) and somebody else “answers” by another sequence of notes or a different phrase.

During this part of the song, most instruments, especially the percussion, have solo sections, time to “free themselves” from the typical patterns they were playing before, and engage in much desired improvisation (which still, mostly, maintains a strong connection to the basic patterns of the instrument);
This is the time for the musicians to shine, basting the full potential of their musical skills, taking their playing to the limit, escaping the timing yet getting back “at the last second”. There might be some additional Coro-Pregon between any given number of instruments, although mainly they play in pairs…

In Timba there might be more gears \ guias during the Montuno section, as an extension of both elements of Coro-Pregon and improvisation during solo sections.

Another element of the Montuno section is the “Mona \ Mambo” section;
This is the solo \ improvisation part for the horn section, during which the Trombones, Trumpets, and Saxophones take charge, and are most noticeable; In Timba you might often hear the main vocalist referring to this part explicitly by shouting “Mambo!”.
Usually, there is no singing during this section.
After this section the song might return to the Montuno section, or have a break happen and go into the ending.

Ending
As Hector says, “Todo Tiene Su Final”, and the salsa song is no exception…
The songs ending much resembles the introduction; It mostly has the main melody, little singing, and the instruments go back to playing their basic \ typical patterns.
This section is also quite short, and is even absent from some compositions.
The “energy level” of the song drops drastically during this section.
Mostly lasts for 4, 8 or 16 musical bars.

So, let us now look at a fine example of how all the various parts and elements of a salsa song come together to form the whole, using the wonderful “Ahora, Que Buscas?” by the talented Havana De Primera…

00:00 – 00:16 : Intro
Short part with no singing, but with the horns playing melody, percussion playing typical patterns, the atmosphere of the song is set, and everything is yet slow and calm.
Lasts 12 (and not 8 or 16) bars, by the way, which is less common.

00:17 – 02:02 : Cuerpo
Starts by having Alexander singing the 1st verse of the song; You can clearly hear the lyrics of the song in a definite manner, the piano plays melody \ support chords (together with the horns which “drop in” once in a while as well) , the percussionists play their typical patterns. After 16 bars of music, at 00:38, the 1st break appears – it’s a Rumba flavoured break (such are in much favor among Cubans), lasting some 8 bars, with a slight horn break on the 6th, 7th and 8th bars of this section.
Another 8 bars in, at 00:59, another break takes place, this time a more Mambo and Son Montuno influenced one, which has a campana playing as well. It lasts 8 bars.
We return to the “regular” cuerpo for some 8 bars more, and then (at 01:21) hear the horns taking charge for a short 8 bar period yet again, with a few small breaks on the 5th, 6th, 7th and 8th bars of this section.
At 01:30 Alexanders magnificent voice returns for another 16 bars of Cuerpo, marked by a slight horn break on their 8th bar and the 1st bar after this section ends.
At 01:51 we have another 8 bars of Cuerpo; then, at 02:02, at perfect unison with the vocals, the Timbalero plays a short break, and the bongocero goes into playing the Campana, marking the start of the Montuno section !

02:02 – 04:59 \ end of song : Montuno
At 02:14 we can hear some Coro-Pregon, with the back vocals stepping in, with an “answer” to the phrase Alexander just skilfully sang.
At 02:25 we have a short horn & percussion break, after which the Coro-Pregon continues at full swing.
At 02:44 there is a series of breaks led by the horns with some percussion, taking place at 02:45, 02:46, 02:51-02:56, 03:03-03:07 .
At 03:07 we have another Rumba break, which lasts ’till 03:16, with Alexander singing a phrase, and the back vocals “answering” him with a phrase of their own.
At 03:38 we have a small Mambo (Mona) section with the horns mingling with the vocals and percussion (and we have a slight percussion solo at 03:51) .
At 04:21 we can hear yet another Rumba flavored break \ gear (guia), ending (and going back to the “regular” Montuno section) at 04:41) .
This song doesn’t have a very well defined ending, but one can hear that from ~05:00, when Alexander sings “se acabo lo que tu esperaba”, the volume starts dropping, and the song slowly fades out into silence…

P.S:

Here is a very useful link – the salsa beat machine, made by Uri Shaked; this wonderful tool allows you to construct a salsa tune from scratch, and has a wealth of musical patterns for the typical salsa instruments…
http://www.salsabeatmachine.org