Downloaded app as a pig in a poke, but was VERY pleasantly surprised. Adds limited dsp effect to audio--near (intimate performance), far (chamber performance), or very far (large concert hall). Seems to adjust L & R channel mix with some slight reverb. Very smooth; a very non-tiring sound that enhances the audio experience for me. Choice of earphone, in-ear transducer, headphone, or speaker. I've used them with B&O earphones (v. 1.0), Etymotic MC4 in-ear phones, and the ipad mini speakers--all are improved with the program.
Two caveats: it won't run DRM files, and the music interface, while very serviceable, isn't as sophisticated as either iTunes or the ipad music player.
Doesn't require dongle or external device.
Worth the price!