Technically a great leap forward

It's interesting that Number 17 and Rich and Strange still suffer from the awful problems of recording and editing early sound, with bad editing and bad sound. Waltzes from Vienna is very much better - altogether smoother and better produced. Does anyone know why? There must have been a technical change around 1933 - when was it first possible to dub music and have multi-tracking?

It's actually very well made and by no means an disaster for Hitchcock. It has a few very typical visual tricks - a visual joke with a servant falling downstairs ending with the top of hishead at the bottom of the frame and another man's legs at the top, also a Hitchcockian shot of Jessie Matthews runningtowards the camera and almaost seamlessly cutting to a close up as she comes through door at a dramatic moment.