I have watch 9 and iphone 12 pro. This has plagued me on older phones and watches too. At some point siri stopped performing this command. For example “siri play africa by Toto”. I can say play Toto or play beatles and it works. I have Apple Music. Works on the phone but not the watch. I can only choose music ny the band name not by song. I am a musician and I use this to practice individual songs using the watch and headphones connected to my iphone. It used to work a couple of years ago. After watch and iphone changes it persists. I know other people have had this issue and tried hopelessly to get help from apple so I haven’t tried. Any updates?