shame about that but a reasonable change would be to use the synthfont64 you got free with BIAB and load a soundfont. i have timbres of heaven and omega. just tried them side by side with an old midi track i have and the timbres of heaven comes close to the TTS1 and so does omega but each has slighly different sounds for the instruments. for example the rhodes piano on timbres of heaven is virtually the same as the TTS1 but the omega patch is more upfront and to me a little more like a rhodes in real life.

all free and reasonably easy to use. try it and if you get stuck post again in the forum.