I'm not familiar with Band Aid II (1989) or Band Aid 30 (2014), so can't comment on those. Band Aid (1984 original) and Band Aid 20 (2014 remake) are exactly the same song, except the remake has a little rap section in the middle.
To my mind, the differences are:
1. Most of the artists who appeared on first one had quite long lasting fame, and seem to have been rewarded with longevity. Only two (George Michael and Rick Parfitt) fell in the great celebrity cull of 2016.
Most of those who appeared on the remake only had short lived musical careers. The only one who is still active and well known is Chris Martin out of Coldplay. Bono doesn't count; And & Dec and Cat Deeley are still going, but they are TV presenters, not musicians. What happened to the rest?
Anthony McPartlin (Ant & Dec)
Declan Donnelly (Ant & Dec)
Tim Wheeler (Ash)
Daniel Bedingfield
Natasha Bedingfield
Busted
Cat Deeley
Dido
Dizzee Rascal
Ms Dynamite
Skye Edwards (Morcheeba)
Estelle
Feeder
Neil Hannon (The Divine Comedy)
Justin Hawkins (The Darkness)
Jamelia
Tom Chaplin (Keane)
2. Musically, the first one is just droning over-layered synthesiser sludge, but the drumming (Phil Collins) is glorious and uplifting all the way through. Musically, the remake is much crisper and well-defined: just piano, acoustic guitar and some nifty guitar solos, but the drumming is really pedestrian and there's a weird bit at the end where they are just bashing some cowbells and hitting sticks together. A pity we can't edit out the rap section (well meant, but jars) and the drumming from the remake and splice Phil Collins' drums in instead.
Debate Magazine
