This is a work in four movements and is also on Luigi Magistrelli and Massimo Laura's 2011 recording of the complete music for clarinet and guitar.
The first movement opens with a slow and ominous introduction in A minor with phrygian inflections builds anticipation for the first theme. We're given A minor moving to F major before setting things up for a swift clarinet tune with sparkling accompaniment by the guitar in A dorian. This theme could be taken as a mutated form of 12-bar blues but for the fact that it's not a recursive theme and leads, as we come to expect from Rebay, seamlessly into the beginnings of a new theme.
Theme 2 in the opening sonata form is, as expected of a more pastoral character than the first theme. The first theme leaned heavily on the dorian mode in the guitar part and on pentatonic gestures in the clarinet. Here in the F major theme we get the clarinet playing a more languid idea but still retaining pentatonic gestures and threading them through diatonic major rather than the dorian mode. The F major section rounds off with a cycle of resolving phrases that wind down the momentum of the exposition to a standstill, something that Rebay seems to have had a penchant for. I'm not always into it myself but it may be your thing and there's no denying Rebay's impeccable gift for writing some wonderful tunes. For a non-guitarist his demonstrated command of the instrument's possibilities is superb.
Now in the recording there's no repeating exposition for this sonata. I don't know if this is because Rebay specified no repeat or the repeat was simply not taken. The development begins with an E minor reprise of the introduction but this passage builds not up to a minor key but to a pleasant surprise, a glowing rush of theme 1 transformed into a witty theme in B major. This leads into a flourish, a busy guitar solo that hints at the introduction again and pauses to give the clarinet a brief solo before rushing back into the recapitulation with the original form of theme 1.
Once again the main theme is back and full of renewed energy. Rebay is so eager to get to his pastorale second theme and have it in A major for his recapitulation he all but skips past any non-modulating transition and takes us quickly into theme 2. He adds a bluesy coda to theme 2 that turns out to foreshadow a return of the introduction, this time as a brief coda showing us we will end this first movement firmly in A minor, not A major. Now is not the time to end with contentment.
The second movement is a set of variations on the folk song from Schumann's Album for the Young. Now I'll admit to not being the world's foremost fan of Schumann and have never been a big fan of the Romantics in general but Rebay gets me to enjoy variations on one of Schumann's themes. The sound of the clarinet and the guitar together is simply charming enough to overcome my personal lack of engagement with Schumann and Rebay has some fun contrapuntal writing.
The third movementis the expected scherzo we find in a traditional classical form. This scherzo is nice and lievely in its outer sections. It's central section is a slower waltz in which the guitar gets a laid-back, jazzy solo. Rebay does a nice job using the central waltz as a way to give the return of the scherzo even more momentum than it already had at the start of the movement.
The finale is a moderately fast sonatina, but not for its brevity. The movement clocks in around six minutes. The finale can be called a sonatina because it has an exposition and a recapitulation but no formal develompent. Rebay opens with a bluesy theme that shifts from major to minor and back to major freely. This rondo shifts into a second theme with a darker mood and the transition back into the refrain comes in the form of a minor key memory of material from the scherzo.
Theme 1 recapitulates but this time with triplets in the guitar's accompaniment, a clever touch to ensure that the returning theme feels new even as it reassures and the guitar's subsequent transitional solo takes up this new pulse. What began as more of a march ends as a waltz, and as so often in Rebay's work darkness ends with light.