This page of the ear-trainer will test your skill at hearing seventh chords, or four-note chords.
The ear trainer deals only with the 5 most common types of seventh chord: Major 7, Dominant 7, minor 7, half diminished 7, and full diminished 7. The full diminished 7 is a chord that is found in the “harmonic minor” scale. Other types of 7th chord are possible, but much less commonly used.
If you are new to ear training, or just have questions about it, you should direct your questions to the IMusiK.ca Music Theory Chatbot. This artificial intelligence chatbot will be able to answer most of your questions. In fact, it was created specifically to work in conjunction with the IMusiK.ca Ear Trainer.
This free online ear trainer also has pages for Intervals (2 notes) and Triads (3 notes).
If you like the ear trainer, or have suggestions for new features, or just comments in general, please feel free to contact me.