I think that almost anybody can become proficient, but talent is something innate. We aren't just blank slates. We are naturally better at some things than others. There have been numerous examples of prodigies who showed amazing skill at a very young age, despite having relatively little practice. For example, Mozart was taught how to play piano from the age of four and was able to compose pieces at the age of five. Many parents have tried to get their small children to play musical instruments from a very young age, but most of them have not been able to produce new Mozarts. Of course, Mozart and other prodigies practiced a lot, too, but others who practiced just as much, if not more, got nowhere close to their skill level.

Now, the reason I said almost anybody is because it makes sense to me that if there are people who are talented, then there must be the opposite, people who have anti-talent. There are people who are so tone-deaf that they'll never make good music, not even if they practice every chance they get. However, talent and anti-talent are at the ends of the bell curve: most people are somewhere in the middle, and if they practice enough, they can make something which is adequate, if not good...and, occasionally, even something great.