See also the advertising for
Epiphone,
Fender,
G&L,
Gibson,
Gretsch,
Guild,
Hagstrom,
Harmony,
Marshall,
Martin,
Music Man,
Ovation,
Rickenbacker,
Vox,
WEM
Vintage Music Man advertisements; 14 adverts covering a period of 5 years, from 1975 to 1980. Click the images to have a closer look.

Black Magic?
Music Man 212HD-130 - 1975

Never Fear Music Man Is Here
Music Man Guitars - 1976

We Came To Play
Music Man Stingray - 1976

For The Music Man Who Hears The Difference
Music Man Stingray - 1976

At Last You Have A Choice
Music Man Stingray - 1976

Music Man Discovers Music Man
Music Man amplifiers - 1976

For The Music Man Who Hears The Difference
Music Man Stingray - 1977

Projection Percusion And Punch!
Music Man Stingray - 1977

When A Better Bass Was Made... Music Man Made It
Music Man Stingray - 1977

Introducing The All New Sabre Guitar
Music Man Sabre - 1978

Come To Where The Action Is
Music Man Stingray - 1979

The All New Sabre Bass
Music Man Sabre - 1979

More Black Magic
Music Man 112 - 1979

One good thing leads to another
Music Man Stingray - 1980
1967 Epiphone Ad featuring a psychedelic fish playing an Epiphone Riviera
1967 Fender Ad - Full Colour Sound
1973 Fender Stratocaster add - The Worlds Favourite Flying Machine
Guitar makers have advertised in music magazines such as Down Beat, Guitar Player and very many more. Some manufacturers advertised widely (Guild, Gibson, Fender) but many more didn't and adverts are few and far between. Here are some of my favourite ads out of the ones i've seen. You can browse through all the images from the category links above, or by manufacturer from the links below.
AMPS
Ampeg, Leslie,
Marshall, Orange, Peavey, Sunn
GUITARS
Epiphone,
Fender,
G&L,
Gibson,
Gretsch,
Guild,
Hagstrom,
Harmony,
Martin, Music Man, Rickenbacker,
Vox