I don't think there is a real acoustic rock era, but acoustic rock has always existed as a shadow form of rock music. There are the obvious references like Bob Dylan and Simon and Garfunkel, but I like the one-offs like "Patience" and "Every Rose has its Thorn". Zeppelin has "Over the Hills and Far Away" which turns electric, and Kansas had "Dust in the Wind". I'll give Guns n Roses credit for inspiring "MTV Unplugged" and Tesla's "Five Man Acoustic Jam" album. A few years later Alice In Chains and Nirvana put their chill acoustic albums out. Are these songs and albums any good or are they just rockers trying to prove their musicianship? Personally I like them because they put focus on the vocals and song instead of speed and volume.