Dance slower? ;^)
Seriously, . . Each track has a time signature showing how long it should take to play. Time it. If what your subjective impression tells you is actually occurring then call 1-800-MY-APPLE and talk to an Apple tech about what may be slowing things down. There should be nothing on your iPhone 6s that would affect the playback speed of an audio file. The device itself is far faster in processing than any audio file. Something sounds fishy here. Check it out.
You pegged me. It's Saturday night, what can I say? :-)
Thanks for the advice!
I cannot think of a logical, digital, or physical reason for music to “play slower”...