Vocal Abilities?
Songwriting Ability?
Musicianship?
Diversity?

To me:

Sign O The Times best displays Prince's diversity because it had him experiment and try different things. There's pop, R&B/soul, rock, psychedelia, jazz, and blues. It was his maturest album of the 80's.

Although Emancipation was 3 discs long and had some diversity, Emancipation best displays Prince's musicianship.

Purple Rain best displays Prince's songwriting skills.

And Finally, Lovesexy displays Prince's vocal abilities.

Vocal Ability - The album. His voice on the ballads are very melodic, the screaming songs have good screams. His falseta is spot on, and his deep voice sounds great. blahblahbalh.

Songwriting Ability - VERY difficult to determine that one. If I had to choose one I'd say Sign of The Times--He used restraint where needed, and indulged himself nicely in other spots.

Musicianship - Toss up between Gold and The Rainbow Children

Diversity - PARADE. Orchestral themes, Funk, Jazz, Rock, Dance, heavily layred sounds, sparse funk workouts,even more sparse acoustic ballads. You name it--he does it and crams it into less than 45 minutes of pure craziness.

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[Edited 2/20/05 21:03pm]

Interesting question!

First of all, I have to mention the For You album. The proficiency he displays - in all of those four categories - is absolutely stunning for a 19-year-old kid! In terms of utilizing his potential at the time, this might be his greatest work ever, IMO.

On the other hand, I guess it's a typical "first album-syndrome", where an artist wants to squeeze in everything they've got, show everything they know, try everything they can think of etc. Later, with maturity and experience, comes often a more sensible, moderate approach, when you don't have as much to prove anymore (to yourself as well as to the audience).

Having said that, let's now look into the categories...

Vocal Abilities?
Pretty much any album, but I go for Musicology - "Life O' The Party" and "On The Couch" says it all. 45 years old and sounding better than ever!

Songwriting Ability?
1999 - full of hooks, lyrically interesting, and sonically so inventive that you almost forget the strong traditional connection.

Musicianship?
For You - maybe not that innovative, compared to later works...but very, very competent!

Diversity?
Parade - other nominees could be SOTT or the Symbol album, but this one has shorter playing time (easier to be diverse on 2 or 3 discs, I figure)

for me the PRINCE album has soemthing special - I can just sit through that without skipping a track....not many other releases I can say that about

1999

The one album that displays his vocal ability, musicianship, songwritng ability and diversity has to be Chaos and Disorder.....THE BEST ALBUM PRINCE EVER DID AND POSSIBLY THE BEST ALBUM OF THE 90'S FROM ANY ARTIST

Vocal Abilities?
I really can't pick one because vocally he is so well-rounded all his albums have great vocal strength and range

Songwriting Ability?
Emancipation for all those truely sincere love songs and Lovesexy for the subtle messages and creativity. I also think Contreversy has some really interesting song writing elements as well.

Musicianship?
The Gold Experience and 1999

Diversity?
Sign O the TImes and Purple Rain

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[Edited 2/21/05 10:58am]

Around the world in a day.

Sign 'o' the times...nuff said.