How is sequencing controlled?

The Transport menu contains commands which allow you to control MIDI Maestro's sequencing engine.

The Transport menu contains commands to begin and to stop playback.  There's also a Pause command, which allows you to stop playback without silencing the notes that are currently playing. Recording is initiated with Ctrl+R.  Use the Stop command (Esc) when finished.  To immediately through out what you've recorded and begin again, use the Retake command (Shift+Esc). Commands exist that allow you to move directly to the beginning or to the end of a song, or from cue to cue, or from measure to measure, or from note to note.  Use the "Go to" command to move to any arbitrary position. Commands to repeat the current measure or to skip the following measure come in handy when other performers "lose" synchronization with the sequencer. If you're working with a set (song list), commands exist to take you to the next or previous song.  A "Revert" command opens the song that you worked with previous to the current song.

Is there a GUI with transport controls?

Yes, the bottom-left corner of MIDI Maestro's window contains transport controls and a "Metronome View":

The circular buttons are (from left), record, stop, play, pause, next song, and previous song.  The horizontal slider beneath these buttons controls the volume, both for MIDI and waveform audio playback.  The vertical slider controls the "tempo multiplier" which is by default centered at 1.000.  You can move this slider up to increase the tempo by up to 2x; you can move the slider down to decrease the tempo by up to 1/2.

By default, the current song's name are displayed, along with the current position and the MIDI meter and key.  The position is given in both measure/beat/tick format, as well as time (hours, minutes, seconds, frames).  Beneath the time elapsed is the time remaining, a count-down timer.  To the right of this display is the current measure and beat number and bouncing-ball metronome.

The small arrows beneath the key/time signature allow you to quickly transpose the song up or down by half-step increments.

Right-click anywhere in the transport area to see relevant commands:

Many of the commands that appear on this menu may be found on other menus; they appear here for convenience. The "View" commands, however, alter the information that is displayed in the transport area:

View set time elapsed/remaining.  This option replaces the clef and key/time signature display with two additional times, showing the amount of time elapsed and yet to go in the set:

Note that the times presented here are exclusive of cues and changes made to the tempo multiplier.

View power spectrum.  The MIDI measure/beat display may be entirely replaced with a power spectrum analysis of the waveform audio which MIDI Maestro is processing:

How can I quickly jump around the song?

Use the "Go to" command (Ctrl+G) to move to any arbitrary position or marker.

Enter a MIDI position by specifying a measure number, a beat, and a tick value.  Enter a SMPTE time position by specifying the hour, minute, second, and frame.  You may select a marker position by clicking on a marker in the marker list.  To jump immediately to a marker without having to click Ok, double-click the marker.

With the Select tool (the arrow icon) selected in the toolbar, you may also click in any view to move the song position.  To move large distances, use the scroll bar at the bottom of a view, then click into the view to position the song.

First, I play in a rock band and was looking for a nice Midi
sequencer that can be use to play live jam/gig and also have FULL
control over the midi. Having a Start button, with TAP for tempo, and
also playing the introduction until I decide to start the song was a
most. Other sequencer I found did'nt give you the control like
MidiMaestro does.--Steve Hollingsworth