Chord Pad is described as 'A chord sequencer with 300+ great sounding styles. Allows you to create chord progressions and backing tracks in minutes'. There are five alternatives to Chord Pad for Windows, Mac and Linux. The best alternative is Band-in-a-Box. It's not free, so if you're looking for a free alternative, you could try ChordPulse or JJazzLab. Other great apps like Chord Pad are Busker (Paid) and Microsoft Songsmith (Paid).
Band-in-a-Box is an intelligent automatic accompaniment program. You can hear and play along to many song ideas and go from "nothing" to "something" in a very short period of time with Band-in-a-Box as your "on demand" backup band.
ChordPulse is a handy backing band software for music practice, inspiration, improvisation, and pure fun with music. Play and sing along with ChordPulse. Use it as a full accompaniment, a drum machine with bass, a metronome with chords, and more.
JJazzLab is a free Midi-based application which automatically generates backing tracks (a musical accompaniment) for any song. It’s a jam buddy to have fun improvising, learn new stuff or just practice your instrument. It’s also a great tool for teachers.
Busker is a complete set of tools to create musical arrangements from sheet music (chords + melody staff). It uses Yamaha compatible styles (thousands can be downloaded for free) for auto-accompaniment.