Well I was a member of Tony Hoffman's Shadows mag years ago and have 'looked in' on this forum for a few years but only recently bothered to join it, hence a few intro postings !
'String of Hits' WAS a chart topper in 1979....following hot on the heels of '20 Golden Greats' doing likewise and THAT - as with Beach Boys, Hollies, Kinks, Dave Clark Five etc ALL having big 'nostalgic' success - slicing right through Punk as if it wasn't there ! - which turned The Shadows firmly into both a more nostalgia based act (in truth they already were as M W & F had discovered back in the early seventies with calls of 'er' Play Apache Hank !' & 'Do F.B.I. Hank !' etc....

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'String of Hits' was o.k. - not a bad album at all in retrospect - I think it was the later Polydor covers albums like 'Simply', 'Steppin to...' etc that really saw them getting rather bland copyists with a very formularised feel to alot of the covers
Yes we can say it made them a bob or two - as self publishers of 'Shadows Music' and penning a good few of their own big hits, 'B' sides of other big hits, having original songs on their big selling albums...plus all the contribution they made on Cliff's hits, penning 'A' side hits plus even getting their songs on a good number of the 'B' sides of Cliff's other hits minus them....
...plus Olivia Newton John having success in the USA and UK with their compositions...
they were surely already a good bit wealthier royalties wise than alot of their fellow artists by 1979 - yes ?
The success of the '20 Golden Greats' in 1977 and then 'String of Hits' in 1979 plus their three UK chart hits did firmly re-establish the band in the public eye - remember after the 'Live in Paris' 1975 set and the 'one off' 1976 single 'It'll Be Me Babe' they had intended folding the band once and for all (hence John Farrar had left with 'Livvy' for the USA etc), but the EMI compilation had caused them to be 'pulled back together' quickly to follow up the '20 Golden Dates' tour
Hence 'Tasty' which Brian Bennett was not happy about - tho' many fans liked it alot - and it was a mix of leftover 'Farrar era' instrumentals (that were dropped from 'Specs Appeal' for the six vocal Eurovision songs I believe) plus 'Cricket Bat Boogie' etc (inspired by the TV commercial)
it does seem odd EMI let them go just as they were back in the public eye, even if largely as a nostalgia act (probably as the new deal proposed would see EMI get alot LESS cash off of them - look how The Beatles got 'ripped off' !)
I think they could have successfully avoided just being a 'covers' band and kept a strong public profile as - Like The Hollies, Beach Boys, Kinks etc - after the success of '20 Golden Greats' they were firmly back as a much loved 'British institution' (& in Europe & 'down under' etc if not in the USA)
Alot of music buyers who preferred the sixties & seventies music to what was being offered by the 80's would have stuck with them - as their concert attendances proved - and while it's true they might not have sold as many albums in the 80's as they did, perhaps the content of the albums they did make might have been all the MORE artistic and critically far stronger ?
bashing out 'modern' sounding covers (that date so fast) might make a few quid but ultimately is creative suicide and really does a band's reputation no favours in the long run...would they if going now be doing albums of 'Shadows Play Lady Gaga' or 'One Direction' covers...?
much as I hate to say it, I found a good bit of the 80's covers and choice of material pretty embarressing at the time and sounded to me like a group of OLDER guys who thought they were still all so very mega hip and 'modern'
- something like a musical equivalent of when you see a old 'Grandad' up doing a 'Michael Jackson' dance routine at a wedding reception...and he's thinking how 'modern' and 'with it' he looks (while the rest of us are cringing with embarressment !!)
SORRY lads but that was how I felt when I heard some of those now hideously dated sounding 80's covers plus 'Shadowmix' etc ...from a CLASSIC influential band that I KNEW were so much STRONGER than merely resorting to doing that kind of thing for the sake of sales...