I can answer parts of this question, but I'm not actually involved with music at Hopkins so hopefully someone else can jump in and help me out

I googled music lessons at JHU and the Registrar's Office gives a pretty thorough response, I hope this helps!

Performance Courses at the Peabody Conservatory

Performance courses at the Peabody Conservatory may either be as part of a grade and credit, or may be audited. Graded performance courses will receive 1 credit per semester unless taken for a double degree program. With the approval of a student’s academic advising office.

Students taking lessons for the first time at Peabody must also complete an Extension Application form which is available in the same locations as the Supplemental Registration Form. Times and locations for Peabody classes are given in the Peabody Master Schedule of Classes, which is available on the Homewood campus in the student’s academic advising office.

Students may take private lessons at Peabody Conservatory with an instructor who is a Conservatory faculty member or a Preparatory faculty member approved by the Deans of the Preparatory and Conservatory. Acceptance is on a space available basis following an audition to demonstrate intermediate or advanced skills. Auditions for Conservatory lessons are held in September. Students will be notified of their audition time by letter from the Conservatory Registrar’s Office. Space in lessons is limited and registration is on a first-come, first-served basis. There is a $165 fee per semester for one half- hour lesson per week. Students who wish to take additional lessons will be charged for them.

The Peabody schedule and deadlines can differ from those at Homewood. Students taking courses and lessons at the Conservatory must check these dates in the Peabody Master Schedule of Courses. Students who wish to take beginning level music lessons may enroll through the Preparatory on a non-credit basis.

This Peabody website is also helpful http://www.peabody.jhu.edu/172

Hope this helped!

Is there a way to register for music lessons online?  The instructions I found seemed to suggest that I need to mail a physical letter to do it - I didn't know that was still done.  Since I'm coming from Israel, anything involving mail is long and cumbersome.  If online registration isn't available, is there perhaps a way to fax it instead?

Unfortunately, no. Every incoming freshman needs to go through the steps of filling out required paperwork and mailing it beforehand during the summer, then auditioning at the start of the fall semester, and then submitting forms to the registrar's office shortly after their audition (if they were deemed advance enough to take instrument/voice lessons for credit at the Peabody Conservatory).

In reply to your questions from your original post:

1. I used to try being a classics/music double minor (before I decided that I wanted to focus more on classics and take several more classics courses than the minor required); in a nutshell, the music minor requires you to take music theory courses (but you can place out of them), music history courses, and private instrument/voice lessons (or participation in a music-based extracurricular activity that's approved as a way for you to fulfill the minor requirement.)

2. How good you need to be to take lessons depends on the instrument you play, as well as how good you are compared to other students auditioning to take lessons in the same instrument.

3. Since I'm a pianist, I've never looked into joining ensembles at the Homewood Campus (I do play the piano for my church's choir here, but that's an entirely different turf, as you could guess). I do know, however, that not every student who has auditioned for a musical ensemble has gotten into one; I just can't gauge whether it's because their competition was steep, the students simply didn't have sufficient musical background needed to play in the ensembles, or a combination of the two factors.