If you want some music playing continuously without any interruption when you move from one slide to another, then you should first make sure that the music clip you are using is suitable for this purpose. A soft music clip that spans across your slides can make the flow between slides smooth, as long as the sound is not jarring or distracting for your audience. Also, if a presenter is going to speak along with the slides — then it goes without question that you don’t want to add a sound that spans across slides. Not only will this make the audience inattentive, but the speaker will be at a distinct disadvantage too. Yet, if you are showing a bunch of successive slides that include pictures — and no speaker is accompanying the slides — then adding a music clip to span across slides may be a good idea — here’s how you go about doing this task in PowerPoint 2011 for Mac.