Hi Damien
Analyzing your songs is highly recommended.
If you load a song the first time it will be analyzed automatically, but using the analyze files button before your live sets in offline player will take that extra workload off your computer while actually DJing.
Pressing the button will always only analyze files you hadn't analyzed before, so once you've done the big pile, just make sur you analyze every once in a while and it will only process the new tracks.
We only use the calculated auto gain value next time you load the song in order to not change the volume of the song while its already playing out loud. (You wouldn't want the audio to drop or increase while the song is playing to the audience). So this is a safety feature ;)
If you have further questions or need help with our products, please create a help request here:
serato.com <- click