Bought these for my wife, as playing loud music around the house is not really feasible in our area. The speakers stick to the belly and the baby seems to enjoy the music quite a bit. We've played all sorts of music to it from Dance to Classical. If there's a negative, I would say that they don't have much base, but I would expect that the noise that travels to the baby's ears is muffled anyway so this is not an issue. Finally we only play music to the baby when it's kicking around a lot, so at to not disturb it's sleep, which is currently 1 hour per day (as recommended). Beethoven gets the most reaction.