Do sequencer programs work like linear tape recorders or are there any that are pattern type sequencers like on an arranger or the motif?

I was also noticing that the S90 comes with SQ01 sequencing software that claims to have arranging functions. What is that all about?

There are all kinds of sequencers. Pattern sequencers / groove boxes and standard midi sequencers. On the mid - higher end of the scale, you have Sonar 3, Cubase SX, Logic, etc and the very high end pro Tools. On the mid to low end of the scale, you have N Track studio, Cakewalk Home studio, Magix Music maker, None of these are pattern sequencers per se, but they do have looping features that allow you to copy and paste, etc. They do work in linear fashion in the way a tape recorder does, but with a lot more options. You can edit note data after it has been played to change many parameters, including location, length, velocity, volume, pitch, to name a few. You can also manually insert new notes without playing and adjust all the parameters.

The SQ01 software that comes bundled with Yamaha workstations and synths reminds me of a lean version of Sonar. It doesn't have quite as many features, but it does a very good job and supports vst instrumrnts and effects. I use it exclusilvely now and only bother with Sonar if I want to work with my Musiclabs midi software, Slicy / fill in drummer and Rythym and chords pro. Otherwise, I prefer the straightforward approach of the SQ01 ( like Sonar it supports 960 ppq of midi resolution and ASIO / WDM audio drivers at 24 / 96 resolution ) My software vst synths play flawlessly in it with no latency issues whatsoever.

The SQ01 does not support arranging functions. Yamaha's previous software sequencer, XG works, does and it allows for step recording with chord recognition using Yamaha styles. One man band is a software program that specifically allows use of Yamaha styles in realtime. You can record the style data in real time along with your own playing, as you would on an arranger.

There is so much to discover with midi and sequencing that I could not possibly give you the tip of the iceberg here. Here are some links that might help you to get a better understanding of it all.
http://www.tweakheadz.com/how_to_get_started_with_midi.html
http://www.recordingeq.com/EQ/req0600/midi1.htm
http://www.btinternet.com/~robin.vincent/midiaudio.htm
http://www.ias.uwe.ac.uk/~a-winfie/teach2003/st_mseq.htm

Here is a site that hosts links to many of the midi sequencers available today. Most of these have downloadable demo "try before you buy" versions, but you may even find a few freeware midi sequencers in there.
http://www.hitsquad.com/smm/win95/MIDI_SEQUENCERS/

Of course, the SQ01 will work fine for you once you get a handle on what it can do.

Best of luck,

AJ