こんにちは! When I first started using katakana combinations to spell foreign words, I was told that there were a certain number of combinations that could be used with small ァ、ィ、ゥ、ェ、ォ to produce sounds that aren’t normally found in Japanese. These being:
ファ、フィ、フェ、フォ、フュ - Fa, Fi, Fe, Fo, Fyu
ツァ、ツィ、ツェ、ツォ - Tsa, Tsi, Tse, Tso
ティ、ディ、デュ、トゥ - Ti, Di, Du, Tu
チェ、シェ、ジェ - Che, She, Je
ウィ、ウェ、ウォ - Wi, We, Wo
ヴァ、ヴィ、ヴ、ヴェ、ヴォ - Va, Vi, Vu, Ve, Vo
My question is - are these the only “officially” allowed katakana combinations? If I tried to make my own that aren’t included on this list, would Japanese people find that confusing? For example, if I wanted to create a “si” sound that was closer to that than シ, could I use something like セィ？Or would that sound be unrecognisable? Has anyone else ever made their own katakana combinations?