Although I've studied Brouwer's Twenty Estudios Simples for the last couple of years, I hadn't heard An Idea (A passacaglia for Eli) until I saw Iliana Matos' fantastic performance. When I begin studying a piece I often reference a particular recording as my standard for the interpretation and I found her performance as recorded by Guitar Salon International quite aspirational. I also used a new method for studying the piece; I evaluated the entire piece off of the guitar before I started to play it and wrote complete fingerings and notes, based on her performance and my proclivities for how I like to mark up my music. It was a beneficial and worthwhile activity and enabled the beginning of studying it much less mysterious, especially for a challenging piece like this one. 

In all the pieces I play I tend to use a performance I admire as a reference point to begin my own interpretation, in this case the performance by Iliana Matos.