Most songs today (as opposed to classical concert music of
yore) are between 3 to 5 minutes long, start off slowly, move
up to speed, pause every now and then, change pitch a bit,
build up the power and end spectacularly.
Live and recorded loopers only know how to replay the loops,
which ones to mute as the music progresses.
I propose an extra controlling interface (on the side) which
will allow you to move it up half a tone in the next round, do
a "speed up" or "slow down", add "fill in" loops automatically
at the appropriate sections, and allow you to have "sections"
and versions of the music (up on top): Prefix, Opening verse,
Chorus, Main, Secondary, Ending and which version for each.
You select the parts to be played in the next rounds, or
directly control what is immediately being heard.
Also, with you left-hand fingers you can dynamically control
the performance, while with your right hand you control a
selected musical instruments and musical "styles", one at a
time, or together.
I envision (if that's the correct term for music) an app that by
moving your fingers along the interface, would cause the
currently playing style to slightly change while holding the
same chord, but putting emphasis or "improvising", giving a
different emphasis on the beats, or changing the order of the