If while walking in the main plazas (squares) in Mexico City you noticed the interesting characters all dressed in their traditional beige uniforms and a cap, manually playing a weird instrument which emits a mildly mistuned sound and wondered who they are, well these are the so-called Organilleros - Organ grinders.
Digging a bit deeper into history, apparently, the organilleros and their instruments arrived in Mexico in the late 1800s from Europe and 130 years later they (only about 250 nowadays) are still a peculiar attraction in the capital where they tirelessly play songs inspired in the Mexican Revolution, hence the use of the soldiers' like uniforms.
These once-ubiquitous characters are now slowly disappearing from the Mexican capital. Back in their heyday, they were apparently hired to play at private events for well-off Mexicans. Nowadays it's quite different, the organilleros are almost seen as annoying or perceived as beggars (which they definitely aren't). The reality nowadays is that these organilleros have to practically beg for money as the younger generations do not appear to pay them any attention, and it's perhaps only the older generations and tourists who appear to occasionally drop some coins in their hats.
I guess we'd not be lying if we said there's not much of an income if you choose this career, however many of the organilleros who still play their weird instrument in Mexico City's squares, have done so for many years and are willing to keep this peculiar tradition alive.