Enescu's 1920 First Quartet crams so much into 45-odd minutes that even two or three hearings barely scratch its surface. It's a veritable forest of invention, fairly Brahmsian in texture, organic in its thinking and frequently dramatic. The second movement incorporates sundry embellishments and effects (including the use of sulponticello), and the finale features variations on a march-like theme. It will make wonderful if challenging listening for anyone who values quality ideas above economical structuring.
Although the two quartets share the single opus number, they're years apart chronologically, aeons if you consider their contrasting styles. The Second Quartet was Enescu's penultimate work, and breathes the heady aroma of Romanian folk music, especially in the slow movement and finale, which recall the world of the far better-known Third Violin Sonata.
Shorter than the First Quartet by almost half, the Second feels tighter and more agile.
The Ad Libitum Quartet do a fabulous job.
They attend to Enescu's endless technical demands with a devotion that translates to apparent effortlessness. Naxos's superior production secures a top recommendation and unbeatable value too.

I'm sure it won't come amiss if I can persuade you to listen to a real sleeper, the disc of Enescu's string quartets.