This Cantabile and March by Sor op. 44 nos. 17 and 18 come from the set of 24 pièces progressives op. 44 which he published in Paris in 1830 or 1831. The March gives practice in harmonics.
The complete set of Sor’s 24 pièces progressives op. 44 is available from Tecla Editions at www.tecla.com as part of the new 2019 second edition of Sor’s New Complete Works for Guitar edited by Brian Jeffery. For details about Sor’s music and his biography, please see www.tecla.com.