Ted deCerchio
In reply to your inquiry about 30's & 40's Sinatra,there's an old Italian saying that says when we're young we have the voice but don't know how to sing; when we grow older we've learned how to sing but no longer have the voice.This is a bit harsh on Frank because when he was young he had a beautiful tommy Dorsey-like-trombone tone to his singing.His early singing was very flowing & connected,or in musical terms,legato.As he learned technigue getting older to compensate for loss of "legato"or tone,he still maintained already good breath control.Frank learned in the early days to catch a breath in the middle of a line,& then carry over the end of the line into the next line. This was perfected as he got older.
Ted Upper Darby

The early Frank Sinatra stuff is really good. It's similar to the 50's and 60's stuff in the sense that he tackled all kinds of music. Lots of Gershwin, Cole Porter, Johnny Mercer, Irving Berlin, and Cahn stuff.

The Harry James and Tommy Dorsey stuff is really swinging and smooth. It's very listenable, but remember back then they didn't have tape yet for recording, so the recordings are scratchy and old sounding which gives them a lot of charactor.

He sings with a different kind of smooth style in the early days.

He became Bing Crosby's rival when Sinatra went solo, so that's the crooner era. Most of it is smooth and slow. But later on in the decade he picked up the pace a bit, and recorded some swinging stuff that's really good. "You Do Something To Me" "When You're Smiling" and "Bim Bam Baby" are all great.

Columbia put out a good record in the 50's of uptempo swinging solo stuff called "Love Is A Kick" and it's excellent. Highly recomended. If you have a record player, you can get a nice copy for 5-10$ , otherwise, see what songs are on it by google, and then download those tracks. You won't be disapointed.