Thanks for the quick replies! I have a master module that uses I2C internally between chips. I don't have control over the addresses of some of these chips (e.g. a dot matrix display from Adafruit). That display has some flexiblity as to address (thx Lady Ada!) but ... I'm integrating this module into a larger system that has a protocol of addresses for different types of modules. thus, to avoid address conflicts, I'm trying to implement and "external" I2C bus in addition to the internal one.
Perhaps I should try to move some of the addresses into a range that is "not likely to be used" (that could bite me later).
Also, r.e. pins. I'm looking at the Teensy LC pinout card. SCL0/SDA0 (in purple) are 91 & 18 respectively. SCL1/SDA1 are 22 and 23 respectively. Am I reading this wrong? I see that 17 and 18 also show SCL0/SDL0, but in more of a shadow form. Does that shadow form indicate that these are available alternate pins for Wire. I guess so. SCL1/SDA1 are default pins for Wire1. Looks like I'll just need to change my board, or use a Teensy 3.2 so that I can do two Wire buses (Wire/Wire1).
Did I get this right?