Song left out on Say You Will...?

[mylittledemon]

Ok guys...here's a tough question. On the VERY BEST OF FLEETWOOD MAC, there is a mini documentary included on the first disc. Now, the band is jamming to some tune at the very beginning of the clip. Lindsey is playing this really cool guitar riff over and over. Was this a song that was cut from the record, or was the band just practicing?

[BlueGrass]

To me I just think they are just in the middle of a jamming session.