You can add as many as you like.
- How are you trying to add the song, dragging or right-click/Add to playlist?
- What happens when you try to add the song to the Playlist, what symbol do you see in the song, or what error message do you see?
- You are trying to add the song to a Regular Playlist aren't you? The one with this icon...
...becasue you cannot add a song to a Smart Playlist, which has this icon;
or a Playlist folder, with this icon;
Are you positive that the Playlist is a Regular one (with the musical note), and not a Smart Playlist (with the cog)? You cannot drag anything to a Smart Playlist. By the way, there is no maximum number of songs for either type of Playlist.
In these screenshots below, I'm in the Songs view, but this is the same whether you are in that, the Artists, Albums or Genres views.
1. Playlists shown in the left panel (by turning it on with CTRL+S).
Right-click/add-to-Playlist should produce a view similar to this:
and you can see in my screenshot that only the Regular Playlists are listed in the right context menu. The Smart Playlists are not listed, because you cannot manually add to them.
2. You can also left-click and drag to the Playlists on the left:
and as you do so, a + symbol appears beneath the dragged item. But if you try to drop it into a Smart Playlist, a red circle with a slash through it will appear in the dragged item as you pass over the Smart ones and the Smart Playlists will not highlight.
3. If you do not have the sidebar showing, if you left-click a song and drag it towards the right of iTunes, you will see the Playlists window slide open on the right:
and only the Regular Playlists are shown.
So - which method are you using, 1, 2 or 3 and what happens?
Okay, I get it about 496, but as I've said, there you can put more than 496 songs into one Playlist:
So at what point does right-click/add to playlist fail?
- After right-clicking, does the context menu appear, with Add to playlist on it?
- If you move the mouse over the Add to playlist, does the list of regular Playlists appears?
- If you move the mouse over the Playlist you want to add the songs to, does that Playlist become highlighted?
- When you let the mouse release, nothing appears to happen. (This is correct.) If the song is already in the Playlist, you should see an error message.
Have you tried the other methods of adding a song to this problem Playlist? If not, try one of them. If that doesn't work, try the third one. What happens?
Since you ask... Select all (CTRL+A), right-click and click Reset Plays, or use my script LastPlayedNever which also resets the Last Played and Last Skipped dates, and clears any Bookmark position.