Thanks , I have a very similar issue with my iphone 4 (recently upgraded to 7.1)
For me the old voice control app just kicks in and the Music App becomes useless. Despite reboots and application restarts the voice contol app continues to randomly switch on for 10 or 20 seconds.
Following on the music playlists become jumpy , play back speeds ups, breaks up and stops.
I have tried full a restore from itunes back ups but with out success. My OS 7 build worked just fine
Have to say I really regret upgrading to 7.1 as key part of the iphone functionality is now useless.
Any advice please ?