The spelling of "am duty" is straightforward when using the International Phonetic Alphabet (IPA). This phrase is commonly spelled as it sounds, with the "a" pronounced as /æm/ and the "duty" pronounced as /ˈdjuːti/. The IPA transcription of "am duty" is /ˈæm ˈdjuːti/. It's important to note that the pronunciation of "duty" may vary depending on a person's accent or dialect, but in general, the word should be pronounced with a long "u" sound at the end.