I believe the fix is a little easier than described above, but still annoying iTunes has such issues. It's simple to do, but as with many such things, describing it clearly with caveats takes a little more effort...
If the "Album Artist" field for any track or album is explicitly set to a specific artist, then all that material will show under a single instance of that artist in Artist view. No other fields need to be set to the artist or otherwise altered to achieve this. However...
The problem is that multiple (supposedly) similar contents of any given field—even if inspected and found to be identical (similar capitalization, no extra/missing/different spaces, punctuation, etc,), even if then in-place retyped, copy-pasted or re-entered via the drop down suggestions menu that appears when you start typing—are sometimes (still) not recognized by iTunes as identical values, no matter how often you verify them or repeat re-entry. The "secret" as others above have alluded to is that the field contents have to be changed to something else, then changed back globally to the desired name, which somehow forces iTunes to acknowledge the box contents are identical. Simply re-entering the apparently correct value does NOT seem to reliably achieve any change in the way iTunes recognizes field contents, as it surely should.
So, while the only field that needs to be altered to amend this specific issue (i.e., repeated artist names in Artist view) issue is the Album Artist field, the same technique will work to correct other grouping issues (fragmented albums for one) where certain relevant fields appear to be correct, but in some hidden way, are not. There is no need to delete/restore or otherwise move any files around to do this (hahaha... for THIS issue, anyway—pre-purchase downloads present some real hair-pullers 🙂).
1. Go to Album view, and search using desired artist's name. This will bring up all whole albums by that artist, and include any tracks from Compilation or Various Artists albums that are in some way associated with that artist (i.e., artist's name appears somewhere in the track info). This also works if selecting individual or groups of albums or tracks other ways, and using the procedure repeatedly, but this is the simplest way to do it all at once.
2. Select all the tracks (click once in tracks area then Command-A, or click on first item and shift click on last, so all are highlighted blue).
3. "Get info" on all selected tracks. (Right click and select "Get Info", or Edit menu—>Song Info. This brings up info relevant to all the selected tracks at once, and allows a global change across all tracks selected, and does not allow editing of any included individual track's info.
(Note 1: If the Album Artist box is blank, or contains an artist's name, following this method will not overwrite/lose any possibly useful additional info that was unique to one or more tracks—minimal concern in proceeding)
(Note 2: If the box shows a grayed-out "mixed", this is because there are already at least two different entries in that field across all the tracks selected. For any given track, empty is counted as a different entry to text. If there are concerns re what unique info may be in the existing "Album Artist" fields, see bottom of post, "Note 3: "Checking Album Artist info, before changing it", before continuing.)
5. Start to type your artist's name in the "Album Artist" box. The pop-up should suggest the (correct version of the) desired artist's name, so preferably select that, rather than type it all manually.
6. Click directly behind newly entered artist's name so text is deselected and cursor immediately follows last character, then type any single letter (e.g., an upper case X or @, whatever).
7. Hit "OK". You may reassuringly see a progress bar pop up momentarily (or not).
8. "Get info" on all the selected tracks again, and delete the extra character (e.g., the X or @) you added in 6. above.
9. Hit "OK". Again you may see a progress bar, as per 7. above.
10. Return to Artist view and you should find all the multiple instances of the same artist have collapsed to just one.
Et voilà 🙂. It seems like it ought to be effective just to skip 6,7 & 8. In the past re-entering an already-existing value across the same field for multiple tracks worked (say to regroup fragmented albums) but it seems now changing it to something else before changing it back—even though nothing apparent was wrong with initial value—is more reliably effective.
(Note 3: "Checking Album Artist info, before changing it". If the Album Artist box shows the grayed-out "mixed" it's possible useful info is present for one or more tracks. It's more likely many are already the [supposedly] correct value and one or more tracks are blank or contain a slight variation on the correct name. Anyway, to check out the unique info:
—Deselect all the tracks in "Album" view.
—Click once on the first (top) track, right-click and select "Song info".
—Click in the "Album Artist" field once to highlight the name there (easier to monitor field contents in next step).
—Repeatedly click the right arrow at bottom left of Info window and watch for any different/interesting values in the "Album Artist" field. You can click it as fast as you can, anything different will jump out clearly.
—Back up to any different entries that arise and evaluate interest, if any. If worth keeping, a cut & paste into the "Comments" box is one option.
—Continue until all tracks have been scanned in this way.
—Proceed back to 1. above.)
vbr
Barry