"Our sweetest songs are those that tell of saddest thought" is an example of -

Epigram: (তীক্ষ্ণ, বুদ্ধিদীপ্ত বা ব্যঞ্জনাময় উক্তি; ক্ষুদ্র শ্লেষসমৃদ্ধ কবিতা বিশেষ।)A brief and witty statement which is apparently self - contradictory.Ex:"Our sweetest songs are those that tell of saddest thought".Here, Sweetest and Saddest oppose each other but as we go beneath the surface level.Paradox: (কূটাভাস; যে উক্তি আপাতদৃষ্টিতে স্ববিরোধী মনে হলেও সত্যবর্জিত নয়)A self-contradictory statement that hides a rational meaning.Ex: "Sweet are the uses of adversity".Source: An ABC of English Literature - Dr M Mofizar Rahman