You are thinking of:
FREE tracks or Promotional Tracks

Bonus tracks are EXTRA tracks not available on the same thing in other formats.

Examples:
Devo's 'Total Devo' casette had two remixes of songs not on the CD. Those were bonus tracks, but only on the cassette.
The Roots The Tipping Point has an additional track on the Euro and japanese versions. Those are bonuses.

Hell, The Smiths and Morriseey, Bjork and Beck and Depeche Mode have half of their "canons" as bonus tracks. But they aren't free.