A four-part progression in C major. Tap any voice to move it to another chord tone — the checker watches for the classic faults and tells you how to fix them.
Rows are Soprano, Alto, Tenor, Bass. Tap a note to change it (the bass toggles octave). Red = involved in a flagged issue.
Parallel 5ths / 8ves — two voices a perfect fifth or octave apart that move the same way and keep that interval; the parts stop sounding independent. Overlap — a voice jumping past where its neighbour just was. Spacing — more than an octave between adjacent upper voices. Crossing — voices out of order within a chord. Leading note — at a V–I the leading note (B) wants to rise to the tonic.