A few suggestions:
Dear Mr Boston,
I have seen your advertisement in a magazine, and I am writing to apply for a job in your music shop.
I am a 17-year-old student from Italy, and I have just finished school. I have always had a particular interest in music, especially Jazz. Therefore, I have a fairly good knowledge of it. Besides, I worked in a music shop similar to yours for a year, while studying in high school and gained useful knowledge about music and the music-selling business.
I guess this could]be a useful experience.Moreover, since I have good English skills eitherboth in writing and speaking, I thinkam confident that I meet the requirements for this job.
In fact, I have just taken the Cambridge First Certificate exam, where I was awarded the highest mark.
I attach my resume to
prove what is written abovesupport my qualifications.
I look forward to hearing from you.