Someone recently suggested a note on a piano I was playing was out of tune. I have a pretty good ear and didn’t agree. Cleartune settled the debate (the note was perfectly in tune — fragile ego saved!). If you’re a musician, this app’s invaluable: a portable tuner with a beautiful rotary interface that lets you play (or sing) a pitch and determine its precise frequency. It’ll also let you calibrate pitches, change notation, transpose notes, switch to a different temperament (of dozens, including Pythagorean, Meantone and French), fiddle with needle damping and switch the pitch pipe waveform…all for just $3.99.