There are many research tools which are also used for teaching the acoustic phonetics of speech rhythm and speech melody. But they were not purpose-designed for teaching-learning situations, and some have a steep learning curve. CRAFT (Creation and Recovery of Amplitude and Frequency Tracks) is custom-designed as a novel flexible online tool for visualisation and critical comparison of functions and transforms, with implementations of the Reaper, RAPT, PyRapt, YAAPT, YIN and PySWIPE F0 estimators, three Praat configurations, and two purpose-built estimators, PyAMDF, S0FT. Visualisations of amplitude and frequency envelope spectra, spectral edge detection of rhythm zones, and a parametrised spectrogram are included. A selection of audio clips from tone and intonation languages is provided for demonstration purposes. The main advantages of online tools are consistency (users have the same version and the same data selection), interoperability over different platforms, and ease of maintenance. The code is available on GitHub.