I saw the 1989 SWEEENY at Circle in the square. Your post points up the danger of watching these archival videos. Yes you see the show but you don't get the experience. It was a good production..with some unique solutions as to how to stage certain sequences. Even so I preferred the original Hal Prince staging - which had just been seen in NY 2 years earlier at New York City Opera.
The director purposely had the actors pull back the performances, since in that setting the audience is close to the action, unlike the original staging in the huge URIS theatre. (I saw it at one of the last previews and the buzz on this new staging was already very strong so the performance had that extra special electricity...something else you wouldn't get from the video.)
I have no idea what you mean by poorly sung, except I did note at the time the reduced company played havoc with the unique harmonies in the chorus songs. Bob Gunton and Beth Fowler were both ideal as Sweeney and Mrs Lovett and Jim Walton sang Anthony's songs exceptionally well.
The reduced orchestration (two synthesizers and a percussionist) robbed us of the rich orchestral textures - and lets face it SWEENEY never sounded so good as on the OBCR - but served the piece well enough., You'd never want an OCR with that reduced orchestra but in theatre it works. Seeing the teeny SWEENEY made me realize that new productions need not mimic the original staging to work, but it was another 10 years before SWEENEY started turning up in smaller community theatre productions. In the end the power of the writing carries the show.
Cast albums are NOT "soundtracks."
Live theatre does not use a "soundtrack." If it did, it wouldn't be live theatre!
I host a weekly one-hour radio program featuring cast album selections as well as songs by cabaret, jazz and theatre artists. The program, FRONT ROW CENTRE is heard Sundays 9 to 10 am and also Saturdays from 8 to 9 am (eastern times) on www.proudfm.com