Pitch Pipe+

Featured by Apple as "New and Noteworthy" on the main App Store landing page. Pitch Pipe+ is a tuner application for the playback of reference pitches, perfect for singing and tuning instruments.
It consists of three views:
Chromatic - Playback of all pitches from 6 octaves. Choose between the note sustaining indefinitely or for 3 seconds. Useful for choirs and a-capella singers as reference for starting note.
Pitch Pipe - This one is for singers used to using chromatic pitch pipes. Sounds are sampled from actual pitch pipes. Choose between C-C and F-F pipes. Tap a currently playing note to kill it immediately.
Guitar - Dedicated guitar tuner lets you tune to guitar samples in addition to the sine wave tone. Auto advance moves down the strings so you don't have to keep reaching for the phone. The following tunings are available: Standard, Dropped D, DADGAD, Open D, Open G, Open A.
The last visited view is shown whenever you relaunch the app so you have instant access to your preferred view.
Calibrate tuning from A = 414 to 466 Hz.
Retina Displays supported.