Musicality is the knowing of the music, and the moving, while dancing, that matches the music. In its simplest form, musicality in tango is stepping “on the beat” in the 4/4 time of tango music, combined with knowing (or hearing) the quicker steps – the syncopation – and stepping to match the music. A large part of tango music is appropriate for simple walking steps; another large part can be heard as Quick, Quick, Slow steps. The “Tango Step” of a century ago was based on the SSQQS pattern, so common in tango music. Basic musicality is being “on the beat”, and synchronizing your quick steps to the QQS in the music.
Tango music also contains more complicated rhythmic elements, such as suspensions, note-displacement syncopations, Habaneras, 3-3-2 phrases, piano accents, rhythmless phrases, and more. Learning these rhythmic nuances, and how to dance to them, takes great familiarity with the music, or possibly writing them on paper. Once you have them on paper, you can listen to the music while reading the paper, and then later, while dancing, it will be easier to hear them and dance to them.
Tango music also contains musical expressions other than rhythm, such as staccato, legato, rallentando, crescendo, diminuendo, forte, piano, chord changes, and Yumbas. These all allow for ways to express the music in your dance movements. Tango musicality is the combination of all these elements – to the extent that you hear them in the music, and dance to them. There is no right or wrong about musicality; just as is true in the dancing, you express what you want to.
So far, this is all about When to step, based on the music; it is equally important when to step based on your partner. If your partner has finished her previous move, settled, and is ready to move, then you need to prepare her to make the next move, and only when she is ready to move can you go. When you both move, and you have led her to step to a certain place, you need to notice where she actually goes, and Follow her. The whole point of tango is Connection, which says that you must maintain your connection with your partner wherever and whenever she goes. This detail is often forgotten in the heat of the dance, when you’re trying to get the figure correct; it would be far better to forget correctness, quit doing figures that interrupt your dance, and connect with your partner. Reconnect yourself with the real reason you are here with this partner.