What form should evidence of a directed study take on a graduate application? I'm planning to send out some applications to a few moderately prestigious Masters programs this fall. I have a lot of research experience, a good GPA, and strong recommendations, but the field I am interested in is somewhat niche. None of my coursework or research relates to it directly, and nobody at my university has this subject as their primary focus. After talking to some professors, I got myself enrolled in a directed study course and have been steadily working through a large chunk of material under the supervision of a prof from a tangentially related field; he's happy to help as much as he can and I'm making good progress.

I've started thinking about what the end result of this effort will be. It seems unrealistic to try to write anything publish-able without having an advisor that is directly familiar with the subject, but the applications I'm going to be filling out tend to ask for some "hard" evidence of research or previous work in the field. I feel that this work could improve my chances of entry, but I am not sure how to best present it in an application. Could I point to a substantial final project of this directed study class as research, or is this too informal of an arrangement for that (since I'm essentially creating my own class on the fly)? Would it be more prudent just to let the name of the class show on my transcript and have mentions of the work in my SOP and recommendation letters? 

Thanks.

(If it's important: My undergraduate work and research is in the realm of  math and comp sci and I'm wanting to enter the field of acoustic modelling.)
I think you should ask your mentors to discuss your research in detail in recommendation letters. Provide them with the language to discuss your research. I would also include it in personal statements and course work.