Firstly, there are 16 bit and 32 bit platforms. DOS is a 16 bit platform, which mostly supports reolutions of up to 640x480. You could go higher if you get enough hardware info on VGA interrupts for the different manufacturers of different video cards. If you develop using a windows based 32bit development you could use directX related stuff and that would probably be you best bet, if assembly must be your choice. If you must start at the DOS level, very little sound stuff is around that can make for good CD quality listening, whereas, Microsoft has had a company contracted to them to write very good sound related wave file stuff. Your best bet is to start with a HLA (High Level Assembler) and use Windows and DirectX. If the process is a learning curve then start with DOS related assemblers and code to get the 'feel of assembly.' By 'basic graphic user interface' do you mean text-like, or do you mean 'graphics' like 'guitars' and 'piano' picture-like, as in 'sprites?'
Basic 'ASCII' art exist and in the DOS days people came up with cute and interesting 'ASCII' art, which was just ASCII characters stuck together made to look like pictures. That would be termed a 'basic graphic' user interface. The other option is spites, whereby you create your own characers by manipulating bit-maps of the ASCII, by susbstitution if you like, and then by similar means stick them together on the screen to form your own graphic.