They tried something. They recorded a new single, "Hallelujah" (which had been a Eurovision pop song winner), but didn't release it with their real names. Instead, the song was put out under the name 'Parker & Penny.' They didn't disguise their voices, once you know who it is, you can clearly hear it. But it was nonetheless kept a secret.
It not only got on the radio, but also started to do pretty well, moving up the charts and hitting #46. Then word finally got out who actually had recorded the song. And airplay dried up.
Whether there is pure coincidence in all this, that the song would have gotten on the air under their real names, and whether it simply reached its peak at #46, who knows? But the circumstantial evidence does seem to support their belief.
Here's the song. I'll let you see if you can figure out who the singers are, and then will post the answer buried down at the bottom after a couple of barricades. If you want to know while listening, just scroll down.
The singers, who recorded "Hallelujah" as 'Parker & Penny' were -- Steve Lawrence and Eydie Gormé.