This whole thing about who needs to be credited for a song is obviously complex and cannot be summed in few lines.
I am currently working on an article about this subject
Some thoughts :
1) Several bands have credited all members on several songs : Pink Floyd on Echoes for example, The doors on their first album, Genesis on their first albums, Yes, Led Zeppelin, etc… so it’s not that rare.
2) I think the point is :
- if the part « composed » by the musician is « important » in the song, then he have to be credited, even if he’s just a studio session musician
- If the part add just a little to the song, then he doesn't have to be credited.
In other words :
would the song sound the same without this part ? and more : would the song had the same success without this part ? would the song be famous in the same way without the part ?
If the answer is yes, then no need to credit the musician, but if the answer is no… then it’s fair to credit him imho
3) Examples :
- 90% of Money for nothing are lyrics, guitar riff, and song structure by MK. Even if the intro is Alan’s idea, it doesnt’ add the « main thing » of the song so to say. It is sureley a nice idea, and yes it adds to the song, but obvioulsy, without this intro, MFN would be a great song though (ok it’s subjectrive, but I guess we all agree about this)
- That’s a different thing with Telegraph road : imagine the song without piano parts... the song would lack his main atmophere and mood. All melodies, chords, harmonies, here and there are not only just « ideas added » to the song, there are mainly the most part of the song. So in this case, I think (it‘s just my opinion), that music could been credited by MK and « arranged by AC » or something like that.
By the way that’s a term that is widely used for other artists, and I think it’s fair for all contributers : composed by… and arranged by…
AC has been credited for strings arrangements on ticket to heaven, like Guy on other songs in Mark’s solo career. So he could also have been credited for arrangement in TR
- Another obvious example : Walk of life. I don’t know whether the keyboard line is from guy, Alan or Mark. But , if it’s not from Mark, it’s not fair to not have credited the musician (Guy or Alan), because obvioulsy that keyboard part is why the song became famous and was a hit. People know this song more for this keyboard line, than for the verses melody or lyrics. So in this case, the « idea » brought by the musician is a part of the composition imho. While the bass line, the drums break or whatever are not that « important ».
- Money is credited to Waters. He wrote THAT iconic riff, the melody, the chords progression and the lyrics. But imho it would be fair that Gilmour should be credited for « arrangements ». If the drums would have been played by another drummer, the song whouldn't have sounded that different, but if the guitar would been played by another guitarist… well you know what I mean.
- Last example : we all know that Terry Williams’ parts on the BIA album have been re-recorded by Omar Hakim. Does it have « changed » the songs ? in term of sound of course yes, but in term on « notoriety » or « success » I don’t think so. That’s why, Omar Hakim can’t claim to be credited because, even if his playing is excellent, it doesn’t add something « noticeable » for the large audience.
That’s how I see the things : Imagine the song without the parts in question, or played by other musicians. Would the song be « the same », or almost « close ».
Depending on the answer, then should be deciding on crediting the musician or not.
just my two cents