https://www.youtube.com/watch?v=hq_CW9EyaGQ

That's from Kevin Macleod, he does most of that royalty free music you hear in most Youtube videos! :D

https://www.youtube.com/watch?v=vZLWS83BHJU

There's another that's a little more upbeat

I am bookmarking his page cause nnng so much music

Incomptech.com has lots of royalty free music, just look under the genre swing for old-timey stuff.

I Just read that as the Indiana Jones theme!

You want Public Domain

https://musopen.org/

http://publicdomain4u.com/

http://www.freemusicpublicdomain.com/

you find the music you like on a youtube just use firefox and the free youtube music downloader attachment on Mozilla. It works well :)

but if they use it in their own video youtube will flag it.

caravan palace, they do electro swing.

My go-to voiced 30s music is always Cliff Edwards ("Fascinatin' Rhythm", "That's My Weakness Now"), just avoid his Disney stuff because obviously that'd have a copyright issue.
https://www.youtube.com/watch?v=FNekUJOlLfA
https://www.youtube.com/watch?v=RVTHhIVXwBc

But if you want instrumental music:

Django Reinhardt is the MAN ("Sweet Georgia Brown", "Honeysuckle Rose").
https://www.youtube.com/watch?v=rwJNuY3i6uQ
https://www.youtube.com/watch?v=mpO5xIltlyU

Jelly Roll Morton ("Sidewalk Blues", "The Finger Breaker") does a lot of swing music and stomps/ragtime.
https://www.youtube.com/watch?v=mFlmUEzaCI8
https://www.youtube.com/watch?v=RYMArK1f7wU

Then if you want a simple standard there is Scott Joplin's "The Entertainer", always a classic. Also "Maple Leaf Rag".
https://www.youtube.com/watch?v=fPmruHc4S9Q
https://www.youtube.com/watch?v=pMAtL7n_-rc

When you think of an inkblot cartoon, most likely you are thinking of a ragtime song, so if none of these appeal to you, just look up "ragtime" and scroll around til you find something that fits the pace. I hope that helps :3

Midnight Crew: https://www.youtube.com/watch?v=ARLPT5rKjWo
It's by eddie morton :D

For the nineteen thirties, you're looking mainly at hot jazz or ragtime, possibly romantic-era classic. I'd expect most if not all of that to have fallen into the public domain by now.

Carl Stalling orchestrated whatever he could find that fit the mood and let Warner Bros lawyers worry about copyright, (naughty fellow.) One of his favourites was "Powerhouse" by Raymond Scott. (But Warner Bros haven't been able to use it since Disney used it in "Honey I Shrunk The Kids.") The tune on every booby-trapped Warner piano is "Believe Me if All Those Endearing Young Charms," (or part thereof.)

Well, someone beat me to it. Scott Joplin is used a lot in old time movies. Remember, in THEATRES back then they had a small organ to plays music. It was pretty much the standard.

There are some good files of old rags on RagtimeDorianHenry's channel on YT