Only certain (skilled) singers are called to "sing along" to a Mariah Carey track.
One must have amazing stamina in all registers, and incredible ease and agility throughout their range. The execution of melisma and precision in pitch control need for songs like "Outside, "Butterfly", "Lead the Way", "Can't Take That Away", "Vanishing" will collapse any lung--Breath control!
Let's not mention her climatic showcases in songs like "If it's Over", "Anytime You need A Friend" and "Vision of Love". The merciless execution of those consecutive chest-dominent F#5/G5s is virtually impossible for a novice (any difficult for most trained singers). It's all about the approach; every note comes out quick and effortless with superb intonation!