IHarmonizer-U is a paid application for recording machining noise, saving the file, and sending it to MLI for a free evaluation (send to harmonizer@mfg-labs.com). IHarmonizer-U is the Unlimited license for the IHarmonizer app. The program detects chatter and suggests alternate spindles speeds to possibly eliminate the chatter. It also will terminate and indicate if there is no stable spindle speed to be found. Please contact harmonizer@mfg-labs.com for any questions Use your IPhone/IPad/ITouch to record machining sound. The application detects chatter if present. If present alternate spindle speeds are suggested to reduce or eliminate the chatter vibration based on user constraints like maximum spindle speed. The user can re-analyze the measurement to get multiple suggestions for spindle speed. The application can be readily used to do accelerate cutting tests on new tooling.