Summary:
When the navigation app is started first and then music is played via Bluetooth, audio quality from Apple Music (and other streaming apps) is noticeably worse than when music is started before launching navigation.

Device tested: iPhone 11, 12Pro, 13Pro, 14Pro

Navigation app: Waze

Cars tested : BMW 5GT 2015, BMW X32017, BMW 420 2019, MB GLC 2017

Connection: Bluetooth (A2DP for media; HFP/SCO may be triggered by voice prompts)

Steps to Reproduce:

Pair iPhone to car head unit via Bluetooth.

Launch the navigation app and start a route with voice prompts enabled.

Start music playback in Apple Music over Bluetooth.

Listen to music audio quality even with voice prompts disabled.

Expected Result:
Music audio quality should be consistent regardless of the order in which apps are launched. Voice prompts should mix or duck volume without degrading the music stream’s codec/bitrate/perceived fidelity.

Actual Result:
When navigation is started before music, music sounds compressed, quieter, or “worse” (reduced fidelity). If music is started before launching navigation, audio quality remains normal. This indicates the navigation app’s early audio focus request causes the Bluetooth stack/head unit to lock into a lower‑quality audio path for subsequent music playback.

Additional Context:

Issue is more noticeable with high‑quality streaming (e.g., Apple Music lossless/high‑bitrate sources).

Likely related to audio focus handling and Bluetooth profile/codec switching when the navigation app acquires the voice channel first.

Observed workaround: start music playback before launching the navigation app; however, this is not intuitive and should not be required.