Streaming music services MOG and Rdio are great resources. They’re not a replacement for music that you license a copy of (because music can disappear from their libraries at any time), but they’re terrific resources for browsing new and catalog music, or providing hours of uninterrupted entertainment.

Both services allow you to search by artist, album or song title, but leave out so many other ways a visitor might try to locate something of interest. Where, for example, are basic genres? How does one find rockabilly or lounge music? MOG lists a record’s genre, but doesn’t hyperlink it; Rdio doesn’t even list genres. Why?

Rdio lists and hyperlinks the record labels (so you can easily find all of the Norton Records entries in Rdio’s catalog), but so many other pieces of metadata are missing. Who’s in the band, and how do I find all the catalog items in which they participate? Who wrote the songs, and where else is their material? And on and on.

Rdio’s New Release  section is painful. 30 per page for 100+ pages, unsortable and unfilterable. They seem to hand-curate the first few pages, so you’ll see artists you know up-front, but as you click onward you’ll find yourself paging through dozens of karaoke records and grey-market reissues.

Serendipity can be entertaining, especially in discovering music, but not by force. Computer systems easily admit multiple indices across a collection of data, so why are the paths of discovery offered by these services so incredibly miserly?

Read a comparison of MOG and Rdio here.