Musical features included added tone chords, modal inflections, unconventional substitutions, and modulations. Frequency hopping can be superimposed on other modulations or waveforms to enhance the system performance. Mozart's piano concertos are filled with assured transition passages, modulations, dissonances, Neapolitan relationships and suspensions. In addition, Zach was fond of adventurous chromatic modulations. The Iraqi santur has, since its inception, been fully chromatic allowing for full maqam modulations. They are also noted for subtle modulations of colour and luminance. Such changes in frequency relevant to social interaction are called frequency modulations (FMs). A common use of the Neapolitan chord is in tonicizations and modulations to different keys. Other methods of embellishing the form include modulations and cadential extensions. Diminished seventh chords and sudden modulations accompany Jesus's apocalyptic prophecies. The song's structure contains multiple key modulations and mood shifts. Differential schemes for other PSK modulations may be devised along similar lines. Secrecy could be realized by making the modulations in undesired directions difficult to decode. Solar output varies on shorter time scales, including the 11-year solar cycle and longer-term modulations. Georgian music is also known for colorful modulations and unusual key changes.