(sorry for my bad english) There is a way to play a sound and sing another at the same time ("double sounds"). It's not easy to play but it's possible (I can play them with my euphonium). In fact, when this "Romanza" was first played, the trombonist couldn't play those double sounds, so music started in measure 11 and finished in 124 with a different Coda. If you want me to send the 'alternative' version to you, just let me know. Thank you for your interest. Juan Ignacio López.