There are enough unemployed musicians. Copyright is a fact of life. Virtually any use of a recording in any presentation, without written permission, is illegal. You can assume any music written since the 1920s is under copyright. You can't grab classical recordings either, because their performances are protected.
Publishers have large and hungry business departments, and they almost always win.
Sometimes they even pay their composers and performers, which is The Right Thing To Do. Even if you're not afraid of lawyers or bad karma, you shouldn't use popular recordings under a presentation. Psychologists have found that people would rather follow the familiar tunes they've heard on the radio, instead of struggling with your more-complicated business message or images. Mix them together, and you lose. MIDI, the Musical Instrument Digital Interface, is actually a Local Area Network standardized by synthesizer manufacturers a few years ago.