Strange sound overlap

I’m attempting to create an animation to go with a song. I’ve read lots of threads and gone about it this way:
- Analysed the song and divided it into sections according to the structure and feel
- Storyboarded the animation in sections to correspond with the music
- Created a scene for each section
- Created some templates that I can use across the scenes.

This all seemed logical (but I’m new to this and comments would be very welcome), but then I think I’ve gone off track a bit.

I created a last scene (not to be shown) and put in it the music file. then (from my earlier analysis using the music editing tool) I copied frames from this (effectively a master music file) and placed them in the appropriate scenes. e.g. the INTRO was frames 0 - 299, Verse-1 frames 300 - 642, Interlude frames 643 - 824 etc.

The music transition between most scenes is OK but not between the intro and first verse. If I play scene1 (INTRO) it’s got a bit of singing at the end which is duplicated in the next scene (Verse-1). This is heard when I use the play button. However I’m positive I haven’t duplicated sound framesbetween scenes, and this is confirmed when I look at the INTRO waveform in the Timeline window, and drag the red pointer along - there’s no singing (i.e. no overlap) then.

Can anyone suggest what I’m doing wrong? If I can’t work it out I think I’ll have to animate in one humungous scene as I can’t risk having the music go wrong.

I’ve been doing more reading and playing around with sound. I realise now that interactive playback may not be in sync with the animation (though I’d like to understand why), however real time playback gives me the same problem.

It’s playing something I just didn’t put into this scene and I can’t work out where it got it from.

While writing this I had a brainwave - what if I’d previously put sound into the INTRO scene and put in too much (i.e. included the bit of voice from the next scene). I might have this left over in a cache somewhere. So… I just created a new file called Trial Intro, copied in exactly the sound frames I wanted and no joy. Playback still gives me the extra bit of voice at the end, and the sound element in the Timeline still shows that all I have is exactly what I want - the instrumental intro.