As a followup, it looks like the problem was with the SoftwareSerial library. I changed over to the AltSoftSerial library (AltSoftSerial Library, for an extra serial port) and the problem with the tone no longer happens.
As a followup, it looks like the problem was with the SoftwareSerial library. I changed over to the AltSoftSerial library (AltSoftSerial Library, for an extra serial port) and the problem with the tone no longer happens.