It is very tempting to write a application that concatenates strings or audio to make a single phrase or sentence. It seems like it would be really helpful if you are squeezed for space or to speed things up. However, natural language is a lot more complicated than you might think. Let's take a straightforward sentence.

The hero kills the monster with his iron sword.

If we change the sex of the character then we also have to change the noun and pronoun:

The heroine kills the monster with her iron sword.

If we change the number, we have to change the noun, verb, pronoun and number:

The heroes kill the monsters with their iron swords.

And that's just English.

Now, if we translate into French, we will also have to inflect the definite article to agree with the gender of the noun and the genitive construction is different from English too.

Les héros tuent les monstres avec leurs épées de fer.

And just to complicate this simple sentence, Swedish appends the definite article to the noun.

a hero               en hjälte            a heroine           en hjältinna
the hero            hjälten               the heroine        hjältinnan

Fun, isn't it? These are very limited examples, but I hope you get the picture. Natural languages are pretty darn complicated. If you plan to localize your software for other languages, just don't concatenate!