Congratulations on your purchase of the M-Audio ProKeys 88. 88 Overview The ProKeys 88 is a stage piano with 14 high. 10-11 of this manual. ProKeys Sono Premium Voice Selection. Congratulations on your purchase of M-Audio ProKeys Sono 88. velocity sensitive 88-key digital piano. ProKeys Sono 88 Quick Start Guide 3 English Third Party Software Configuration With ProKeys Sono connected to a computer, any MIDI or audio capable. M-Audio ProKeys Sono 88 Digital Piano in Box. 88 Semi-Weighted Keys Stereo-Sampled Premium Steinway Sound. Manual. Pick up in store.