Okay, I do not know about castrati political parties in India, but musically, the castrato was important to late Renaissance and Baroque music, particularly opera.
In a nutshell:
Castration (orchidectomy - is that the word?) of young boys prior to adolecense was a way to preserve the higher pitched lyric quality of the voice, since, in general, girls and women were not allowed to perform in church or on stage. Trouble is, the voice still often broke after the operation, so the boy was useless as a singer.
As far as the ones who sucessfully retained the voice, there were quite a few well-known castrati - IIRC, many of Handel’s operas were written particularly for a couple of famous ones (whose names I cannot recall). From what I’ve gathered from my opera history classes, there were about the equivalent of the stereotypical prima donna - commanding high fees for performing, rights to change the music as it suited them, – one in particular insisted that his first entrance be on horseback from the top of a hill, whether or not the scene called for a horse or a hill, if he was gonna sing in the opera, he got his horse and hill and armor (did I mentioned armor was part of the contractual obbligation? It was.). Several stars had quite a following of female fans, too. (Hey no worries about offspring here, just plain old fun. Again, my OpHist books are at home, and I can name names there. IIRC, Rossini was about the last composer to write a role specifically for a castrato, since by then (1800s) women were acting and singing onstage - ironically, women were often in “pants roles”, playing the part of young adolescent boys, i.e. Cherubino in “Le Nozze de Figaro”.
As far as making new ones, highly unlikely in this country. There is a recording of the last surviving operatic castrato, recorded on 78 prm, before his death iin the early 20th Century. The voice takes a while to get used to it, particularly picturing a 6 foot tall man singing like an 8-year-old choirboy.
Now please do not mix up the castrato voice with another legitimate male voice type called the ‘counter-tenor’, nor with the ‘falsetto’ voice. In both cases, the men are intact.
The counter-tenor is a higher-pitched tenor (best example is the guy who sings on many of the P.D.Q Bach recordings [John ‘Somebody’, humorously listed as ‘bargain counter-tenor’]). My college did a performance of Berstein’s “Chichester Psalms” - the 2nd movement calls for a child (a very innocent and lyrical part), but the conductor brought in a counter-tenor - about the same voice range as the child, but with the musical maturity needed for the piece.
Falsetto is “head voice”, where the performer is reaching for the higher notes in his overall range. Using chest voice for the upper range would be too heavy quality and bad vocal practice. (Frankie Valli does a lot of falsetto in his performances.)
(Chiesu, I just previewed and gotta learn to type and think faster!)