I went to Cakewalk's "Knowledge Center" and read recent instructions for installing both 64- and 32-bit Sonar at same time. However, must have been for higher pedigree version of Sonar, because "Command Center" permitted an uninstall, but not a re-install of both...so I picked 32-bit.

TTS-1 dll then did show up under Pgm Files (x86) - 32-bit version - as expected. Then I was able to virtually plug in some guitars & keyboards and enjoy some mighty fine MIDI pickers in BIAB!

You're right, shouldn't be too hard to get 64-bit SHS working as well, but I'll save that for another night. Thanks for all your help and encouragement!