The chords we use in the songs mainly help to “color” the background on which the melody develops.
Depending on the choices we make we will be able to enhance a melodic passage and create the right atmosphere in the song.
In the context of major keys we have a specific chord that plays the role of creating tension: the dominant seventh chord built on the fifth degree of the scale.
If we wanted to create “artificial” tension in our progression, it is possible to use other dominant chords, unrelated to the key, which temporarily carry out this task:
this is the case of the “secondary dominants” which we talk about in this new appointment.