Artists that use the same song structure...

+2 for Frogman. Blues consists almost entirely of 12-bar or 8-bar forms, although the older generation often ignored (or lost track of) the time count, when they felt like it ("Lightnin' strike where lightnin' want." Lightning Hopkins.) SRV achieved amazing variety within the limitations of the form, but it was done mostly via the solos, in his live shows. His albums are pale reflections of what he could really do.

Pride and Joy was admirably original, for a blues. No real argument about I'm Cryin', but in live performance, you would never confuse the two.

When someone told Jimi Vaughan that Stevie never played anything the same way twice, he replied, "Stevie never plays anything the same way once!"

Bdp, Sorry my wrong: Bluegrass has 2 types of songs: in minor and in major the rest is same.

How about the vast majority of contemporary country coming out of Nashville--songwriters there have made "reppropriation" a fine art. Case in point...this revealing mashup on YouTube.

Another 100 % agreement, this time with Marty. I imagine all Baroque also sounds quite similar to those who have yet to hear past the outside surface. Form is only one aspect of music, but yes, the first one heard and recognized. Inside the form are many musical ideas that share only that basic form with one other, just like Blues, Bluegrass, but NOT contemporary Nashville "product"!

I have been listening everyday for the past month to two different recordings of C.P.E. Bach's Six Symphonies, trying to, first, "know" them completely (I'm not there yet), and second, to appreciate the differences between the two performances (Pinnock and Hogwood). THAT I just last night got, pretty much.

Contemporary Country is similar in lyrics:
She's bad bcoz she left me and I feel blue
or
He's bad bcoz he left me and I feel blue