This is a love song that keeps asking a nervous question. It opens gently with "Siéntate y déjame escuchar tu voz" (sit down and let me hear your voice), and then turns into something about making music itself: he wants to know "en qué frecuencia está la inspiración" (on what frequency inspiration is), the kind the time gives you "para armar una canción" (to put a song together).
The chorus is the heart of it: "Siendo que estoy bien quiero más" (even though I'm fine, I want more), followed by "Y aún no sé muy bien si esto duraría hasta el final" (and I still don't really know if this would last until the end). That doubt is the whole song. Notice "duraría", the conditional of durar (to last): he is not saying it will last, only wondering if it would. Later the request gets simpler and more desperate: "No me dejes caer donde sea que estés" (don't let me fall, wherever you are). And "déjame bajarte el sol" (let me bring the sun down for you) is a lovely twist on the Spanish idea of promising someone the moon and the stars.