I Was The One is a ballad song recorded and performed by artist Elvis Presley. It was released as the B-side of his major hit single Heartbreak Hotel, released in 1956.
The arrangement is in the key of C, but features a few chords out of the key as well.
The strumming could be either done in cut time with swing feel or in 6/8 . Personally I prefer the latter, which might be a tad harder to execute, since the right hand moves much faster.
We also take a look at how to somewhat copy the electric guitar riff in the intro.