B737-800
Flight Crew Last 90 Days 399
Situational Awareness; Human-Machine Interface; Confusion; Communication Breakdown
Deviation / Discrepancy - Procedural Other / Unknown
Air Traffic Control Issued New Clearance; Flight Crew Became Reoriented; Flight Crew Requested ATC Assistance / Clarification
Human Factors
I was the flying Pilot Flying. We were getting vectors from Approach for the ILS/Visual Approach. Approach had us set up on a base leg approximately eight miles southeast of a fix waiting for the intercept heading to join the final approach course. We queried Approach when we crossed the final approach course without further instruction. That's when we realized that #1 VHF was unknowingly or accidentally switch to Tower frequency. We were told; by Approach; to climb to 4000 ft. when we switched back. Approach vectored us back for the Visual Approach. The approach and landing was uneventful.
[Second narrative contains no additional information.]
B737 flight crew reported they inadvertently switched from Approach to Tower frequency and flew through the final approach course.