Slowing down speeding up

Cubase
1

Hi,

One of the pieces I am working on (mostly overdubbed acoustic) guitars seems to have developed a strange quality recently where when all tracks are played together it sounds as if it is slowly speeding up in the first 30 or 40 seconds, as if playing on a dodgy vinyl or tape player. Such that it’s not until about 10 seconds in that is is possible to discern the key. One of the guitars is reversed. The effect is subtle, but noticeable, maybe around a semitone over around 20 seconds. What could be causing this and does anyone have any similar experiences?

2

Audio track?

3

Yeah, everything is audio. I wondered if there was maybe a glitch in the bouncing down process as some of it has been edited and bounced down (via the ‘edit’ tab not export) more than a couple of times. Although it’s a cumulative effect - I can’t notice it on individual tracks.