Not so much the signs, but the jingles from radio commercials. One that pops into my mind at times is the old BromoSeltzer line:
"Be wise, by Bromo Seltzer, Bromo Seltzer, Bromo Seltzer."
The words Bromo Seltzer were spoken/sung in a raspy, whispery voice with increasing rapidity to sound like a steam locomotive getting underway.
Bob Wright