This suite of six MIDI sequencer tools run as AU-only plug-ins within a suitable AU-host. Rozeta also makes use of one of the new features Apple has snuck rather quietly into the iOS 11 update: the ability for AU plug-ins to send MIDI Out data.
Alexandernaut’s Fugue Machine arose from its creator’s interest in the music of Baroque composer JS Bach. It is a multi-phasic sequencer, offering up to four playheads capable of independent motion across the same musical landscape.
Apple's loop-sequencing application has grown up, with the addition of sophisticated recording, editing and mixing facilities, a powerful waveform editor, and many of Logic's most sought-after effects.
Flagship sequencer apps are so packed with features that it could almost be a full-time job learning the package of your choice. If your needs are simpler, why not make it easy on yourself and investigate one of many options that are more entry-level or cut-down, yet still remarkably capable?