Personally, I would not release a cover song for free over the internet. The nature of the digital world is that data doesn’t disappear. Over a period of time, even at a couple hundred a year, the downloads would add up and at some point the copyright owner could demand the mechanical royalty for each download.
Ok, so you bang out “Proud Mary” on the acoustic, put it up on Blogger and forget about it. Ten years later a bill arrives to remind you that the page is still there and that you have been accumulating debt the entire time.