Strange situation

I was on reddit earlier, typing a post when my file downloader (IDM) Popped up. Normally this happens when I am on a page that has some type of media on it. Except I had done nothing to download or anything.

The file in the downloader window was an MP3 file:

hxxp://mp3joker.com/download/7ac87bef9e6e5ea4fb058fce57d81f266453af9c/1/edith-marquezmi-nombre.mp3

File scans clean in VT, however securi reports the mp3joker site is infected with JS malware.

Now, this wouldn't be surprising if I just had been navigating to a site, but I wasn't really doing anything to cause this, any idea what caused this file to start trying to download?