In most web browsers you can listen to the intervals and tunings described here.  Wherever there is slight or distinct colour in a table you can click on the cell to hear a note or notes.  Right click (two finger tap on a MacBook, touch and hold on Android, etc.) for an alternative.  For intervals the alternate click plays a chord whilst the primary click plays a note sequence.  For single notes the alternate click may render the note in a different octave and for note sequences the sequence is reversed.  Try it!

This feature is known to work in Firefox and Chrome on the PC, MacBooks, and Android on a Samsung Galaxy.  Unfortunately, due to a lesser degree of audio support, it does not work in Internet Explorer, Safari on a PC or on older iPads.  You will need good quality headphones or speakers; all of the examples use pure tones and some use low frequencies so you may not hear it all on laptop speakers or inner ear headphones.

Advanced readers may like to know that the reference pitch for each page can be changed.  By default the reference pitch is A = 440 Hz but this can be changed by appending to the end of the URL in the address bar, for example ?A=432 or ?C=256.  Where a note other than A is used the offset from A will be calculated using equal temperament.  You need to do this for each page.

Technical specialists may wish to turn on the browser debug log to see the actual frequencies of notes being synthesized.