Dropping the last letter of a verb in some cases?

Question

I have been listening to some Italian songs lately and I have noticed a fact that I don't know if it's a rule or it's done only in the spoken language of the song to improve the flow of the song.For example, in the song "*Gli Anni*" by 883, at some point it says:> Gli anni del "Tranquillo, **siam** qui noi"Regarding what I know about Italian, shouldn't it be "Tranquillo **siamo** qui noi"?----------Another example, in the song "*Il bello d'esser brutti*" by J-Ax, the title shouldn't be "Il bello d'**essere** brutti"?----------Another example, and the last one, in the song "*La canzone del sole*" by Lucio Battisti, it says:> Ma quante braccia ti hanno stretto tu lo sai per **diventar** quel che seiShouldn't it be "per **diventare** quel che sei"?----------I want to know if this is some kind of rule that I don't know and also applies for the written language, or if it's just a spoken trick to make it sound better. In any case, I would like you to explain me when we have to use this form or the another. Since I'm learning Italian and these kind of things confuse me a lot.

Answer 1

The dropping of the last vowel of a verb is called apocope. Apocope is not limited to verbs and is done for sound, metric, and style reasons.

fil di ferro - filo di ferro

amor - amore

mar - mare

signor - signore

dir - dire

andiam - andiamo

or - ora

Val d'Aosta - Valle d'Aosta