I wouldn't care if it was a copyright infringement. I'll infringe day and night if I feel like it. Stealing stolen property from thieves is a victim-less crime.
But hold up. So how is a riff any different than a chord progression? How is Stairway to Heaven just a generic chord progression that anyone can use, apparently, but a "riff" is "signature" and therefore untouchable?
.......
There's too much gray area and loopholes in this shit.
No there aren't really any "loopholes"...but there are times when an interpretations/ruling needs to be made.
The Library of Congress and performing rights organizations have all agreed on what can be copyrighted and what can't...based on music theory and what it takes for a *song* to be a *song* VS what are pieces of chords (and even notes to a degree) that constitute generic music that has no complete *song* structure, and therefor can't be copyrighted and/or CAN be reused.
It's just chords, but those are signature identifiable simple progressions that make you know what those songs are.
I know we've all seen/heard this before...but it again demonstrates that you can write a thousand songs that have *similarities* (some very close similarities) but are in fact individual songs and no one is suing anyone over it.
That's 73 songs...all the EXACT same chord progression...some even have "similar" melodies that run the entire lengths of the songs, but not enough to constitute copyright infringement. There's some formula...it has to be X number of notes for a certain length of time...etc....or something like that.
1 . Journey – “Don’t Stop Believin’”
2. James Blunt – “You’re Beautiful”
3. Black Eyed Peas – “Where Is the Love”
4. Alphaville – “Forever Young”
5. Jason Mraz – “I’m Yours”
6. Train – “Hey, Soul Sister”
7. The Calling – “Wherever You Will Go”
8. Elton John – “Can You Feel The Love Tonight” (from The Lion King)
9. Akon – “Don’t Matter”
10. John Denver – “Take Me Home, Country Roads”
11. Lady Gaga – “Paparazzi”
12. U2 – “With Or Without You”
13. The Last Goodnight – “Pictures of You”
14. Maroon Five – “She Will Be Loved”
15. The Beatles – “Let It Be”
16. Bob Marley – “No Woman No Cry”
17. Marcy Playground – “Sex and Candy”
18. Men At Work – “Down Under”
19. Jill Colucci – “The Funny Things You Do” (Theme from America’s Funniest Home Videos)
20. Jack Johnson – “Taylor”
21. Spice Girls – “2 Become 1”
22. a-ha – “Take On Me”
23. Green Day – “When I Come Around”
24. Eagle Eye Cherry – “Save Tonight”
25. Toto – “Africa”
26. Beyoncé – “If I Were A Boy”
27. Kelly Clarkson – “Behind These Hazel Eyes”
28. Jason DeRulo – “In My Head”
29. The Smashing Pumpkins – “Bullet With Butterfly Wings”
30. Joan Osborne – ” One of Us”
31. Avril Lavigne – “Complicated”
32. The Offspring – “Self Esteem”
33. The Offspring – “You’re Gonna Go Far, Kid”
34. Akon – “Beautiful”
35. Timbaland featuring OneRepublic – “Apologize”
36. Eminem featuring Rihanna – “Love the Way You Lie”
37. Bon Jovi – “It’s My Life”
38. Lady Gaga – “Poker Face”
39. Aqua – “Barbie Girl”
40. Red Hot Chili Peppers – “Otherside”
41. The Gregory Brothers – “Double Rainbow Song”
42. MGMT – “Kids”
43. Andrea Bocelli – “Time To Say Goodbye”
44. Robert Burns – “Auld Lang Syne”
45. Five for Fighting – “Superman”
46. The Axis of Awesome – “Birdplane”
47. Missy Higgins – “Scar”
48. Alex Lloyd – “Amazing”
49. Richard Marx – “Right Here Waiting”
50. Adele – “Someone Like You
51. Christina Perri – “Jar of Hearts”
52. Crowded House – “Fall At Your Feet”
53. Red Hot Chili Peppers – “Under the Bridge”
54. Daryl Braithwaite – “The Horses”
55. Pink – “U + Ur Hand”
56. The Fray – “You Found Me”
57. 3OH!3 – “Don’t Trust Me”
58. Tim Minchin – “Canvas Bags”
59. Blink-182 – “Dammit”
60. Kasey Chambers – “Not Pretty Enough”
61. Alicia Keys – “No One”
62. Amiel – “Lovesong”
63. Bush – “Glycerine”
64. Thirsty Merc – “20 Good Reasons”
65. Lighthouse Family – “High”
66. Red Hot Chili Peppers – “Soul to Squeeze”
67. Banjo Patterson – “Waltzing Matilda”
68. Bic Runga – “Sway”
69. Ben Lee – “Cigarettes Will Kill You”
70. Michael Jackson – “Man in the Mirror”
71. Mika – “Happy Ending”
72. The Cranberries – ” Zombie”
73. Natalie Imbruglia – “Torn”
....and nd then here's some more using the same basic chord progression to at least start off...and then they might drift into something else....which is what you have with "Stairway to Heaven", and that's what makes it a different song from "Taurus", and why there is no real copyright infringement, IMO.
https://en.wikipedia.org/wiki/List_of_songs_containing_the_I–V–vi–IV_progression