Lossless and compressed are not opposites. An audio file can be compressed while allowing the original audio data to be reconstructed completely. FLAC and ALAC are examples. Lossy methods take a different route to reducing file size. This distinction concerns data storage; it does not by itself explain how a recording was produced or whether a particular playback sounds preferable.

What lossless actually promises

The FLAC documentation describes compression that preserves the audio data. Decoding restores the corresponding input signal. A packed document provides a useful analogy: saving space need not mean removing sentences. Audio compression uses properties of the signal to represent it more efficiently.

The promise concerns the data supplied to the encoder. If those data already came from a lossy file, saving them as FLAC does not recover information previously removed. A larger file therefore does not prove a better source. Origin and format need to be considered separately.

Keep three properties distinct

File format describes how data are organised and encoded. Resolution, such as the sample rate and bit depth of a PCM signal, describes other properties. Production determines which recording, mix and processing are stored in the first place. Two releases may use the same format yet sound different because they originate from different treatments.

File size is not a universal quality rating either. Duration, channel count, resolution and encoding all influence it. Under comparable conditions, a long piece generally takes more space than a short one. That says nothing about its sonic value. Avoid comparing arbitrary files solely through their number of megabytes.

Lossy encoding serves another priority

Lossy formats such as AAC or MP3 reduce data through encoding that does not preserve all the original audio information. Whether a particular difference is audible to you depends on the material, encoding and listening conditions. A format name alone cannot establish an honest personal listening result.

For your own comparison, use the same source recording and a comparison copy made from it. Two unrelated releases of the same song may differ before encoding begins. Hear appropriate short passages at comparable volume and, where possible, without knowing which file is playing. An uncertain or unrecognised difference is also a useful result for the conditions tested.

Keep an archive copy and a portable copy separately

For long-term storage of your own music files, a lossless main copy can support later conversions. A smaller additional version may suit a device with limited storage. Label both clearly so that the portable copy does not accidentally replace the only preserved source.

Avoid repeatedly converting one lossy version into another when the original source remains available. Make new listening copies from the retained main file where possible. This provides a coherent workflow without requiring detailed knowledge of every encoder setting. Back up the files too: an appropriate format does not prevent accidental deletion or drive failure.

Consider the complete playback path

A lossless download does not guarantee that every subsequent transmission stage also remains lossless. The actual device combination must support the required connections and settings. Apple's guidance distinguishes offered file quality, storage requirements and connected-device capabilities. Check the combination rather than inferring the whole chain from an icon in the player.

Three questions are enough for a practical decision: are you preserving a source, saving space or investigating an audible difference? Each requires a different check. Keeping these aims separate avoids both storing every album in the largest available version and dismissing format as meaningless. What matters is whether the chosen file reliably serves its purpose. Record that purpose alongside the collection's organisation rules, particularly if several versions will coexist.