A method for processing audio signals in a radio transmitter, includes: receiving an analog audio sample stream and a digital audio sample stream; determining offsets in time between the analog audio stream and the digital audio stream using a normalized cross-correlation of audio envelopes of the analog audio sample stream and the digital audio sample stream; filtering the determined offsets in time to produce filtered offset values; determining an alignment slip adjustment value as a function of the filtered offset values; aligning the analog audio sample stream and the digital audio sample stream using the determined alignment slip adjustment value; and generating a hybrid radio signal for broadcast that includes time-aligned analog audio and digital audio.