Hey,
The HQ button allows you to access expertly engineered equalizer settings curated for specific headphones that make everything sound better.
We had a an error in our last build (whoops!) that kept the HQ slider showing even without headphones plugged in, and it generally disappeared if slid without headphones in.
I would highly suggest checking out the newest version of Songza which fixed that. Now, when you plug in a pair of headphones, you should see a box prompting you to choose your make and model. Subsequently, the HQ box will now only show when headphones are plugged into the phone.
If you have any more Songza questions send me a PM.
Cheers,
Jason/// Mobile Platform Management @ Songza