And now we're in 1931, with more Bosko and the introduction of a new series! All of these cartoons were directed by Hugh Harman and Rudolf Ising.

Big Man from the North
Mountie Bosko is given the task of arresting a dangerous criminal. While this short still has a lot of focus on music, the series seems to be evolving, with this short clearly having more of a plot and conflict than the previous ones.
8

Ain't Nature Grand!
And this is more like the earlier Bosko shorts, with a lot of small gags involving insects and other animals Bosko meets in the forest. Cute but not the most spectacular, apart from a pretty imaginative last couple of minutes.
7.5

Ups 'n Downs
The focus is clearly starting to move away from musical sequences into funny gags, which is a good thing. Hot dog vendor Bosko participates in a horse race with quite an unreliable mechanical horse.
8.5

Dumb Patrol
This war-themed cartoon is a combination of earlier and later Bosko – in his plane, he fights the unnamed villain who already appeared in a couple of cartoons, but there's also a musical sequence where he tries to impress Honey. The former sequences are far more interesting.
7.5

Yodeling Yokels
Bosko and Honey in the Alps, including a lot of yodeling, of course – maybe too much yodeling. But still some entertaining gags, especially one involving an owl.
7

Bosko's Holiday
Bosko and Honey (both more talkative than before) go on a picnic. The sequence with Bosko's phone and alarm clock is easily my favorite gag in this one.
7.5

The Tree's Knees
Bosko is in a forest, but the focus is as much on the anthromorphic trees and animals as on him. Cute and fun in its simplicity!
8

And here's the start of the even more music-focused sister series, Merrie Melodies. Joining the Looney Tunes and the less successful Song'Nata series, it would continue for almost four decades. From now on, Ising will direct the Merrie Melodies and Harman the Looney Tunes (i.e. the Bosko cartoons).

Lady, Play Your Mandolin!
At first, the two series had genuine differences – instead of Bosko, the first Merrie Melodies star is Foxy (a pretty obvious Mickey Mouse rip-off). He may not have much of a personality, but the short itself is a standout. Foxy goes to a café where various (drunken) antics ensue while everyone sings the title song – a really catchy one! The best effort so far, and promising for the future of the series.
9

Smile, Darn Ya, Smile!
Train driver Foxy has various problems along the way. Some scenes in this are very similar to some of the earlier Bosko shorts, but it's still an entertaining short. The most memorable thing in this short is the song, though!
8

Bosko Shipwrecked!
After a storm, Bosko ends up on an island and meets not only another lion but also a tribe of cannibals. A fairly ordinary entry in the series.
7

One More Time
Foxy is having some nice cartoons, and the third and last one (making him the first character to stop appearing in the series) is the best one yet! This time he's a police officer fining and arresting criminals. The music works well (almost all the dialogue here is sung) and the characters' antics are fun and at times surprisingly violent!
9.5

Bosko the Doughboy
Another war-themed Bosko – this time he's in the infantry, mostly trying to avoid enemy fire with his friends. The most action-packed and violent Bosko cartoon (even including apparent deaths!), also less singing than usual.
8

You Don't Know What You're Doin'!
Replacing Foxy, Piggy is the new Merrie Melodies star. He goes to a jazz concert with his girlfriend Fluffy, heckles the performers, starts performing himself, gets heckled by a group of drunks... This one features some surreal sequences and visuals involving drunken characters. For some reason, the Merrie Melodies are almost consistently more interesting and experimental than the Bosko cartoons – and jazzier, too!
9

Bosko's Soda Fountain
Bosko works at a soda fountain, making ice cream dishes for his customers. Sadly, one of them is Honey's piano student, Wilbur the kitten. Not my favorite in the series, especially the scenes with the aforementioned annoying brat.
6.5

Hittin' the Trail for Hallelujah Land
The first of the infamous Censored 11, removed from circulation by then-owner United Artists in the 60s due to perceived racist content (although this one seems quite tame to me). Piggy, making his second and last appearance, is on a ship with his girlfriend Fluffy who gets abducted by a typical movie villain, while her uncle Tom ends up in the graveyard where he is threatened by a group of skeletons. Piggy has to save both. Not quite as good as the earlier Merrie Melodies, but another nice jazzy soundtrack, and again more eventful than most of the Boskos.
8

Bosko's Fox Hunt
The first Looney Tunes cartoon about hunting! With the help of a horse and a dog, Bosko is chasing a little fox, but they all keep getting outfoxed by him. A lot of chasing, probably the closest in spirit to the later cartoons, though they would obviously improve on this one.
8.5

Red-Headed Baby
With Piggy not being used anymore (apart from the end titles), the Merrie Melodies will be one-shots from now on. At Santa's workshop, a doll (the red-headed baby of the title) is kidnapped by a spider, and a Napoleon doll has to save her. Quite fun – and why are all the songs in these so catchy?
7.5

For shorts not released in the Looney Tunes and Merrie Melodies series, 1931 is a pretty bad year – most of them are extremely rare if not completely lost. The Song'Nata (formerly Spooney Melodies) series of animated/live-action organ performances had four more entries before being discontinued, "Just a Gigolo", "Say a Little Prayer for Me", "When Your Lover Has Gone" and "For You", but none of those are available for viewing anywhere (though they may still exist in archives).

At the time, Warner Bros. also distributed a few cartoons not made by the Schlesinger studio.

Buster Bear may have been rejected by Schlesinger earlier, but creator/director John R. McCrory managed to get WB to distribute one of his shorts anyway, to little success.

Buster Bear
Buster is hosting a revue at a town hall, featuring various acts. Some of them (like a pair of dancing ducks) are liked by the audience, while others get a worse reception. In style, it's quite similar to the Harman-Ising cartoons and many others of the era. Interestingly, it even uses the same theme song ("A Hot Time in the Old Town Tonight") as the early Looney Tunes. The animation quality is slightly worse though decent, but the voice acting is weak. An interesting curiosity if nothing else.
6.5

WB also released "Graduation Day in Bugland", a Listerine ad possibly made by Fleischer, and "'Neath the Bababa Tree" and "Put on the Spout", supposedly Terrytoons productions based on Dr. Seuss' Flit ads, but these commercial cartoons all appear to be lost.

The second year already shows strong improvement, though there are some weaker entries in the bunch. The Merrie Melodies are much more fun and surprising in general, while the Looney Tunes seem to rely largely on Bosko as a somewhat established character. Will this remain the case in the future?