Combining multiple audio files into a single continuous track involves several technical processes that happen beneath the surface of what appears to be a simple concatenation operation. At the most fundamental level, digital audio files must be decoded from their compressed formats into raw PCM (Pulse Code Modulation) sample data before they can be merged. This is necessary because compressed audio formats like MP3 and OGG store audio in encoded frames that cannot simply be appended to one another—the frame boundaries, header information, and encoding parameters would create audible glitches and corruption at every junction point.

Once decoded to raw samples, the audio streams must be reconciled in terms of their technical parameters. If two files have different sample rates—say 44,100 Hz and 48,000 Hz—one must be resampled to match the other through a process called sample rate conversion. This involves interpolating new sample values using mathematical algorithms, typically polyphase filters or sinc interpolation, to create samples at the target rate without introducing aliasing artifacts. Similarly, files with different channel configurations (mono versus stereo) must be matched, either by duplicating a mono signal to both channels or by downmixing stereo to mono.

The crossfade transition between merged tracks is an elegant application of amplitude envelope multiplication. During a crossfade, the outgoing track's amplitude is gradually multiplied by a decreasing gain curve while the incoming track's amplitude is multiplied by an increasing gain curve. The two resulting signals are then summed together sample by sample. The shape of these gain curves—linear, equal-power, or logarithmic—significantly affects how natural the transition sounds. Equal-power crossfades maintain consistent perceived loudness throughout the transition by using complementary sinusoidal gain curves, preventing the perceived volume dip that occurs with simple linear crossfades.

Gap insertion between tracks involves generating silence—samples with zero amplitude—for the specified duration and inserting them between the decoded audio streams. The number of silent samples equals the gap duration multiplied by the sample rate: a one-second gap at 44,100 Hz requires inserting exactly 44,100 zero-valued samples per channel. After all audio streams are decoded, reconciled, and joined with the appropriate transitions, the combined sample data is encoded into the chosen output format, producing a single file containing the complete merged audio.