Centerline vs gStrings

Centerline is a chromatic tuner for identifying played notes and seeing whether their pitch is flat or sharp. Its chromatic range is 62–800 Hz and follows the nearest note, including sharps and flats. Players can choose Simple, Trail, Strobe, or Workbench displays; Trail shows six seconds of pitch history. Guitar mode detects a string automatically or lets users select one, and includes standard tuning, All Strings progress, and a headstock view. Tuning works offline, and pitch analysis takes place on the device: microphone audio is not recorded, saved, transmitted, or shared. The free Chromatic plan includes the core tuning functions and guitar views. Centerline Complete costs $3.99, paid once and adds alternate and custom six-string tunings, capo settings, A4 calibration from 432–446 Hz, and reference tones. The app is available for Android, iPhone, and Mac. It has no ads or account system; optional usage analytics are disabled until enabled and then exclude audio and pitch data.

gStrings has no write-up on Specifiction yet; its figures are above.