There's a CD Nickelodeon put out in 2001, called "The Newest Nicktoons." Surprisingly, the CD has some music clips from on-air promos of back in the day, some going back to the 1980s and many from the early-mid 1990s. Sample clips are at Walmart.com, but I'll post the classic stuff here-
-this one is the classic "Nick nick nick nick nick nick nick nick, Nickelodeooooon!"
-this is from a 1985 short on-air promo where the aliens are flying around in space and singing something like, "Doesn't matter where you are, we make Nickelodeon where-ever you are. Better off by far! Nickelodeon, Nickelodeonnnnnn"
-this one was one of the most surprising... this one is called "Nick's Top of the Hour" which was used from 1985-1987 when the announcer was announcing the date and what's coming up next right before YCDTOTV in the mid 1980s (of course, the announcer's voice is not on the clip, only the music). I couldn't believe Nickelodeon still had that in their archives.
-this is my favorite clip. This is a montage of some of the "Coming Up Next" commercials from 1993-1995. The announcer's voice, where he said what's coming next and followed by, isn't there, only the neat music Nickelodeon used. That second cip from the montage was used for YCDTOTV's "Up Next" commercial when it was on for one hour on Saturday mornings!
-the music heard here is from the same period as what's right above. These were used for the commercial bumpers ("________ will be right back" / "And now back to ________").
-this is an new remix that contains some sounds from the old 1985 on-air promos, including the singing dinosaurs, the singing WB frog, and the aliens as mentioned above.
-another remix that contains sounds from more old 80s on-air promos, like the singing fruit, singing dinosaurs, and jungle animals.
-another updated remix like above, but contains sounds from another old 80s on-air promo, the one where animals were singing down the road and walk into a TV set.
-I don't recall this one or what commercial/clip this was used in, but it sounds 'classic' to me, probably from the early-mid 1990s.
-like above, I don't remember this one right off, but it sounds like another classic, from the early 90s.