Caló is a mixed language that has emerged from contact between Spanish and Romani over the past six centuries. As part of a process which is quite natural and common in all situations where languages come into contact , Caló has taken on the grammatical structure of Spanish and inserted Romani vocabulary into it. In other words, it has undergone a process of relabeling in which the functional category tags have become Spanish while most of the lexical categories have remained Romani. It has virtually lost its original grammar and inflection and replaced them by Spanish grammar and inflection. It does, however, preserve a rich lexicon. Most Caló lexicon therefore has a Romani etymology, even though it contains some loanwords from other languages .
Caló is a collective creation of Spanish Roma. In other words, it is a language that emerged in Spain from where it travelled with the Roma to Hispanic America and there took other paths.
Some authors such as Bakker claim that the Calão of Portuguese Roma emerged in Spain and from Portugal went to Brazil where it became Calon.
We know that in the south of France there are groups of Roma originating in Spain who also speak Caló.
In Spain the best known, or rather most researched, variants are Catalan Caló and Andalusian Caló. Presumably there are others but they have not yet been documented.
As the famous linguist, lexicographer and lexicologist Julio Casares pointed out, Caló is a true natural language and can be seen as the Spanish variant of the Romani language.
It may be that the Spanish Roma progressively created Caló due to their relationship with the non-Roma world. It should be remembered that in spite of persecution, the degree of integration of Roma in society and the majority culture is greater in Spain than in any other country not just near us but possibly in the entire world. In other words, Caló comes from the convergence and encounter between Roma and non-Roma in Spain.
Following Fernández Ortega we can distinguish between documentary Caló, the one which has been collected in Caló dictionaries, and contemporary Caló, i.e. the Caló which is actually written and spoken today by Roma people in everyday life.
“It is hard to address the problem of the current actual state of Caló among Spanish Roma, because we are at a very advanced stage of a long process of disintegration, close now to total extinction,” wrote Professor Carlos Clavería in his Notes on Spanish Roma in 1962. George Borrow also branded Caló as the “ruins of a language” in his book The Zincali (1837). Indeed, and unfortunately, both authors were correct in their claims, though not entirely as Caló is still alive! It continues to be used in everyday life.
Today Spanish Roma continue to speak Caló because it is recognised by most Spanish Roma as the language of our community. Yet Caló is still today a language in regression and obvious danger of extinction. If the fundamental mission of any language is communication, Caló long ago ceased to be useful for this. While its use is limited to shrinking areas (family, family celebrations, social interaction with other members of the community, etc.), it is also true that it retains a strong identity and emotional value, i.e. it is used to identify ourselves as Roma to other Roma, and that based on this initial identification the relationship is placed on the map of the community, of us, of solidarity. But Caló is losing relevance even for this first identification. Currently you only need to use a phrase in Spanish related to religious worship  and you will be admitted to the community.
Caló is still used in everyday conversations but only in a token way to emphasise a particular aspect or (and why not?) to be cryptic so that people around us do not know what we are talking about.
There are no books or magazines published in Caló. Some publications have their title in Caló. But there is nothing else.
There are very few Romani singers who have recorded a song in Caló. There are even choirs /simple_tooltip] in Caló, some of them very wellknown and celebrated by believers. But there are too few of them for Caló still to be considered as a language of artistic creation.
Because flamenco is an art created to be sold to an audience consisting mostly of non-Roma, there are very few songs composed solely in Caló. The use of words in Caló is a stylistic device to give the song itself an aesthetic touch that makes it sound more flamenco because it sounds more Romani. Most of these Caló words used in flamenco are Romani expressions, i.e. loanwords from Caló but which are part of the rich flow of general Spanish and hence obviously are widely known by the audience.
The etymology of the names of flamenco palos or musical forms is still insufficiently researched. In some cases the Romani origin is more than evident: arborea (from the Romani e bora, for the bride), bulería (from buxlo, large), debla (from devla, God!), giliana (from gili, song), soleá (from sovlax, through the Caló solejar, solemnly swear). In others it is more questionable, such as tango (from tang, narrow) and siguiriya (from na sig gila, slow songs).