The Yamaha Synth Arp & Drum Pad still seems to be free. It is a multitimbral Yamaha XG quality rompler. Not bad for a free app:

https://itunes.apple.com/us/app/synth-arp-drum-pad-us/id530320055?mt=8


Nord Stage 3 sw73, Yamaha CP88, KeyB Legend Live, Kurzweil PC3K7, EV ZXa1 + sub. K&M stands, Hammond E112, Leslie 3300, EHX V256, Roland SE-02, Yamaha EX5R & TG77, Novation Nova desktop & much more...