Picture the scene, you are about to hit a heavy leg session and your first exercise is squats. You have your headphones and you have your playlist ready (because you are prepared and ready) and the music selection is fast paced to keep you fired up for the session. This fast tempo music keeps you pumped for the heavy exercises while you lift the weights. I think you will all agree with me that you will choose this type of music over a slow ballad to get you ready for squats.
Now picture this. You finish your heavy compound exercises and perform isolation exercises but you change your music playlist. Since you need to really focus on squeezing the muscles during isolation movements, why not adjust your music to slower tunes to help slow everything down. Keeping fast paced music during isolation exercises could result in you speeding the exercise up when in fact you might need to slow it down. Give it a try and let me know what you think :)