Dear Giulia, 

I like this inventory and it is possible to apply it to your purpose:

The Beck Anxiety Inventory (BAI), created by Dr. Aaron T. Beck and other colleagues, is a 21-question multiple-choice self-report inventory that is used for measuring the severity of anxiety in children and adults.The questions used in this measure ask about common symptoms of anxiety that the subject has had during the past week (including the day you take it) (such as numbness and tingling, sweating not due to heat, and fear of the worst happening). It is designed for individuals who are of 7 years of age or older and takes 5 to 10 minutes to complete. Several studies have found the Beck Anxiety Inventory to be an accurate measure of anxiety symptoms in children and adults

Each question inquires about how bothersome a symptom of anxiety has been for the subject over the past month. Scoring the BAI is based on a 0-3 point scale, with each question being scored as follows based on participant response:

0 points: NOT AT ALL

1 point: MILDLY: It did not bother me much.

2 points: MODERATELY: It wasn't pleasant at times.

3 points: SEVERELY: It bothered me a lot.

The point values of the chosen answer choices are then summed to produce a total measure score. The BAI has a maximum score of 63.

The following criteria indicates the severity of anxiety based on the total score:

0-21: low anxiety: this score suggests a healthy level of anxiety, but could also result from the ability of the subject to mask their anxious symptoms or if the subject is in denial of such symptoms.

22-35: moderate anxiety: this score suggests that the individual should work to identify triggers of anxiety symptoms and try to manage anxiety through stress-reduction techniques.

36-63: severe anxiety: this score suggests that anxiety symptoms could be potentially harmful to the physical and/or mental well being of the individual. Consulting with a professional may be beneficial if severe anxiety continues

I took this from Wikipedia

I advise to use ECR-R, ECR-R has two important scales: avoidance and anxiety.

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There are several self report questionnaires that specifically measure music performance anxiety (MPA). Kenny's K-MPAI has good psychometric data, and there's also a version for adololescents. I doubt that it has been translated into Italian. 

Kenny, D. & Osborne, M. (2006).  Music performance anxiety: New insights from young musicians.  Advances in Cognitive Psychology, 2(2-3), 103-112.

Another questionnaire that has been used in many MPA studies in the literature is  Nagel et al's Performance Anxiety Inventory (PAI)  - although I have not yet found psychmetric data for this tool.

Nagel, J. J., Himle, D. P., & Papsdorf, J. D. (1989). Cognitive-behavioral treatment of musical performance anxiety. Psychology of Music, 17, 12-21

I hope that's helpful!

Best of luck

Susanna