An interesting sort of update to the classic player piano design –
The sequencer plays the notes as a arpeggiator, i chose for this playback method because i dont have a midi device that can play 24 keys at the same time.. There are 2 different arpeggio modes. One rearranges the playback sequence to the active notes velocitys. And the second mode changes the arpeggio playback speed to the amount of notes that are active. If this mode is not selected the playback speed is set by a potentiometer. These modes can also be combined.
The sequencer has 24 LDRs that are read into 3 ADC ports of the arduino, via 3 4051 ics.