For multipitch I have a tip: First, record yourself singing (doesn't matter how good/bad are you at it). Then check that how high you can reach naturally/comfortable and how low. Then you look at the pitches and if them are for example highest C5 and lowest A3 then 4 pitches (2 pitches between C5 and A3) but if smaller range then just 3 or 2 pitches. Sorry if explaining doesn't make a sense