But why do they need them? (warning, litteral answer ahead)
Because the makers of the app want to use location to obtain better quality adverts for the financial return of their app. (or at least, their agents/brokers who place the ads want to do that on their behalf).
If you are playing a game or an app with litte monetizable intention-orientated behavior (eg a shoe shopping app would have shoe orientated adverts) then you need to use something like location to at least get one dimension of context.
If you don't want the GPS locations going up, perhaps you should buy the paid version of the app (most do have a paid, no-ad version).
Reasonable explanation. However the paid version of SoundHound still requests location permissions. One would hope then it would only be used as they claim, for storing history locally and the data would not be sent over the network.
Anyone fancy sniffing the traffic from a paid version to see if it is still sending GPS data?
Maybe they use the location information to improve their service (i'm really just imagining here).
You hear a song somewhere, a club, a bus, wherever and Soundhound is able to identify it. Somebody near you hears the same sound, but Soundhound can't identify it, maybe it is to noisy, the sound to low, for whatever reason they can't tell you what song it is, but they have the good recognition from somebody close to you, so they might be able to narrow it down...
Again, just hypothetical, that's just what i would do from an engineer's perspective, i'm almost sure, they are not doing anything fancy like this.
I thought this article in the NYTimes was interesting because it revealed that music identification software companies have former talent scouts working to identify new, trendy music before it goes mainstream.
SoundHound claim location information is "saved with your searches in History to help you remember where you heard the song. This can be disabled under Options." http://www.appbrain.com/app/soundhound/com.melodis.midomiMus...
... which is a nice idea, but why does it need to transmit your coordinates over the network?