The 15 Song Album collection:

01 - Travelin' Light - J.J.Cale
02 - Interstellar Overdrive - Pink Floyd
03 - A Horse With No Name - America
04 - A Ship On The Wind - Salyu
05 - Night Train - Visage
06 - Truckn' - The Grateful Dead
07 - Magic Carpet Ride - Steppenwolf
08 - Walking to New Orleans - Fats Domino
09 - Bike - Pink Floyd
10 - Riding The Waves - Steve Harley & Cockney Rebel
11 - Trans-Europe Express - Kraftwerk
12 - The White Ship - H P Lovecraft
 
01 - Travelin' Light - J.J.Cale
02 - Interstellar Overdrive - Pink Floyd
03 - A Horse With No Name - America
04 - A Ship On The Wind - Salyu
05 - Night Train - Visage
06 - Truckn' - The Grateful Dead
07 - Magic Carpet Ride - Steppenwolf
08 - Walking to New Orleans - Fats Domino
09 - Bike - Pink Floyd
10 - Riding The Waves - Steve Harley & Cockney Rebel
11 - Trans-Europe Express - Kraftwerk
12 - The White Ship - H P Lovecraft
13 - Rocket Man - Elton John
 
01 - Travelin' Light - J.J.Cale
02 - Interstellar Overdrive - Pink Floyd
03 - A Horse With No Name - America
04 - A Ship On The Wind - Salyu
05 - Night Train - Visage
06 - Truckn' - The Grateful Dead
07 - Magic Carpet Ride - Steppenwolf
08 - Walking to New Orleans - Fats Domino
09 - Bike - Pink Floyd
10 - Riding The Waves - Steve Harley & Cockney Rebel
11 - Trans-Europe Express - Kraftwerk
12 - The White Ship - H P Lovecraft
13 - Rocket Man - Elton John
14 - Beam Me Up - Pink
 
01 - Travelin' Light - J.J.Cale
02 - Interstellar Overdrive - Pink Floyd
03 - A Horse With No Name - America
04 - A Ship On The Wind - Salyu
05 - Night Train - Visage
06 - Truckn' - The Grateful Dead
07 - Magic Carpet Ride - Steppenwolf
08 - Walking to New Orleans - Fats Domino
09 - Bike - Pink Floyd
10 - Riding The Waves - Steve Harley & Cockney Rebel
11 - Trans-Europe Express - Kraftwerk
12 - The White Ship - H P Lovecraft
13 - Rocket Man - Elton John
14 - Beam Me Up - Pink
15 - From A Window Seat - Dawes
 
I don't think any could be done it posthumously, at least without some serious smelling-salts😳.

Seriously though, some clarification on subject, both singers must have died from the time of recording to song release or just both singers are dead now. The former might take weeks to finish.

One singer dead at time of recording and ' there ' via electronic ' trickery ' , not to be confused with songs released after death that had been recorded but unreleased ( cos they were crap ) then released after death to cash in :D