ColinW What would be really cool is COLLECT function similar to what Adobe uses when saving an InDesign File or ProTools does. It finds all files used and packs them into a folder. I use some of the same audio files for different playlists and often will change the key or speed depending on who I'm gigging with.
You already have this capability, the one file can be used or not used in multiple songs .
Just DUPLICATE the same song , change what you need to change on the duplicate & change its colour only if you don’t want to change the name of the song then group all those coloured songs you want and place them in to the same colour playlist now you can have all white songs you normally perform with all players and all green same songs that are in a green playlist name, are you songs without the bass player, this is very simple to achieve plus you can use FILTER to gather all songs you require to make a playlist and you have visual colour confirmation to what song has what preferences you desire so you can mix and match songs on the night if your bass player is unavailable for the next bracket you can use the white version of the same song knowing the bass is there, you can also use the artist column and label it NO BASS this will give you colour confirmation plus actual writing confirmation in you song list when selecting songs and the FILTER function makes it simple to find all your files you need to select one or all to play or to create a full playlist which could be your whole gig without the bass player.
This does not use up any extra memory as the data files are not duplicated , the same file is used on all your duplicates it’s the changes to every version that gets saved and this does not use a lot of data.