Introduction:
The author finds himself unable to tear away from the square because of the sweet flute music being played there. The melody captivates him and he is engrossed in the enchanting tunes. This is the main reason that keeps the author hooked to the square.

Explanation:
The author's inability to tear away from the square is primarily due to the sweet flute music that he hears. The melodious tunes played by the flutist captivate his attention and create a mesmerizing atmosphere. The author is enchanted by the music and finds it difficult to leave the square because of its captivating effect.

The flute music creates a sense of joy and tranquility in the author's mind. It brings a peaceful ambience to the square and adds to its charm. The author is drawn towards the music and finds himself lost in its beauty. The sweet melodies evoke a sense of nostalgia and create a soothing atmosphere that the author finds irresistible.

The author's fascination with the flute music is also evident from the fact that he describes it as "sweet." The adjective used to describe the music indicates the author's admiration for its beauty and the impact it has on him. The sweetness of the music adds to its allure and makes it even more difficult for the author to tear himself away from the square.

In addition to the flute music, there are other factors mentioned in the options given. However, these factors do not hold as much significance as the music in captivating the author's attention. The other options like the availability of food, a magic show, or the author buying flutes may be appealing but do not have the same enchanting effect as the sweet flute music.

Conclusion:
In conclusion, the author finds himself unable to tear away from the square because of the sweet flute music being played there. The melodious tunes create a captivating atmosphere that the author finds irresistible. The music brings a sense of joy and tranquility, making it difficult for the author to leave the enchanting square.