This might be part of the 16.3 firmware fiasco where compilations are incorrectly indexed.  Not sure though because it sounds like your boxset is the same artist for all 4 CDs.  What is the name of the boxset?  Maybe try changing the subfolder names to “(Boxset name) one”, (Boxset name) two etc.  But… read on.

 what I have done to boxsets in my library is put all the tracks in one Album subfolder and make the track numbers 01-whatever.  If the artist is the same for the entire box set just make sure the Artist & Album Artist tags are exactly the same.  My folder structure is Genre - Artist - Album - Tracks.

Hi MoPac & thanks for your reply & assistance
The boxset is by IQ “The IQ Weekender 2024” which as I said is a 4x CD set
I have uploaded a few screenshots of how the file structure is in my NAS & how it comes up on Sonos App on my laptop (which is replicated on my Android phone)
Does that help further?
Paul

 Listening to Dark Matter from Qobuz now.  Good Prog. 
 
 I guess if it was up to me I would have the folder structure Prog Rock - IQ - The IQ Weekender 2024 - (Tracks 01-28).  Tags would reflect this structure.  Artist tag would be IQ, Album Artist tag would also be IQ.  Album tag would be the same as the album folder name.  The only other tags I use are Track Name, Year, Genre.

 Not sure what you use to tag.  I use DbPoweramp.  So the tag naming may be different on whatever tagger you use.  Just make sure the Artist & Album Artist tags are exactly the same.

 You should be able to also do this with the 4 albums.  Just make sure the Album tag matches the name of the album folder for each of the 4 albums.  When you search Sonos for IQ it should show those 4 albums + the others you have by the artist IQ.  Just keep the Artist & Album Artist the same in all those albums.  Usually for rock jazz etc that is automatic, but classical can be a mess so I make sure the Artist & Album Artist tag are both the last name of the composer.

Hello @MoPac & thanks again! - Glad to hear you are enjoying some vintage IQ prog! - If you like all their stuff, they are releasing a new album (it’s been a six year wait since “Resistance”) - Probably 2025 as this year is nearly over …

Anyway, back to my problem - I have never paid attention to tags, but it looks as if I will need to do so in future as far as Sonos is concerned? - I buy most of my music via download, using Bandcamp if possible as they pass more funds to the bands than others? - I do still buy some CDs which was the case with this IQ Boxset, mainly as it was not on any download sites (that I could find?) - So I burned my own flac files - Would you recommend I delete all the album files my NAS, then edit the tags & then reload them again? - Take a while with 4x CDs but the mess they are in on Sonos makes that necessary?

 No.  Edit the tags in the physical folders on the NAS.  Is the Music folder on the NAS Mapped to your computer so you can easily access those folders.  What is your tagging software?

Hi @PaulBoy1313 , when you ripped the CDs did you set the tag Disc#s? Having this tag blank would, in my experience, result in the listing you're getting with all the T1s, then all the T2s etc. 

You might like to go in with whatever tag editor you use and set the Disc# tag, at least for the first track from each cd, and see what happens. If you do the whole lot, you should see whole collection in the correct order as a single Album, as Sonos groups tracks with the same Album name together, then in Disc# then Track# order. It takes no notice of the folder structure you use.

Hope this helps. 

Hi @jreddaway & thanks for popping in - I’m using Mp3Tag to edit & it has a “Discnumber” tag? - Is that the one you are referring to above? - It isn’t tagged on my 4x CDs so do I tag each CD with the corresponding discnumber i.e. CD1 all tracks Discnumber is 1 / CD2 Discnumber is 2 etc?
Sorry for the thicko questions, this is all new ground for me?

Spot on, @PaulBoy1313   Go through the tracks, reindex and see what you get. You've got nothing to lose!

Hi again @jreddaway - I have reindexed the 4x CDs & they now appear in my Sonos Music Library as one list of tracks in the correct order! - Very happy with that & also a big thank you to @MoPac for suggesting I map my NAS music folder which was 10x times quicker than the way I was doing it!

Thank you guys 

Good news, @PaulBoy1313   Glad it worked for you, just take care that you don't become obsessed by tags like me!

 If your into classical tag obsession is a necessity.

Now that's a real rabbit hole you're opening up, @MoPac . I like to keep things simple - the Composer tag is my key thing with classical material. 

Definitely not obsessed, but......

 The reason I never used the Composer tag was when I started all this digital music stuff there was no Composer category on some of the controller software.

@MoPac 

Iirc, you have tagged your classical material with the composer's name in the Track title. Have you used MediaMonkey?  There's a very powerful RegEdit extension for it that I'm sure you could use to populate the Composer tag from the Title & then remove the name from Title. Once you get the hang of it, it's very fast indeed. 

Perhaps something to play with during the long winter nights.....

 No.  I do not put the composer name in the track title.  I put the composer’s last name in the Artist & Album Artist tags.  This assures that no matter how controller software looks for the artist I will get the correct result.

 I use DbPoweramp for tagging & JRiver Media Center for playlist creation.