The Sing & Play sub-series had a precursor in the album Motortown Hits from 1970 (listed under 'Compilation LPs') which brought together a themed set of recordings. Sing & Play though was properly launched in mid-1971 with a Beatles tribute. Several more would follow, collecting together hits made famous by popular artists of the day.
For all bar the last of these albums, it was necessary to make new recordings so as to have enough songs for an LP. Some 29 new recordings appear in the series.
Amazingly, a 'new' LP which slots into this series was released in 2018, by Electronic Sound magazine. There is no connection to Hallmark/Pickwick as far as we are aware.