SynthEdit is not a sequencer. To record your own music you need a Sequencer as well. A good list of sequencers is available at http://www.hitsquad.com/smm/win95/MIDI_SEQUENCERS/
Record your music using a separate sequencer, save it as a standard MIDI file
(*.mid).
In SynthEdit, load the MIDI file into the 'MIDI Player' module. It's big
advantage is the elimination of MIDI timing problems. SynthEdit's
internal midi connections transmit 'instantly'. This very high speed
offers rock solid timing, better than ANY hardware MIDI setup.
Use SE with your sequencer
Use a 'MIDI loopback'. This separate piece of software redirects your sequencer's MIDI output to SynthEdit's MIDI input.
A good free loopback is Hubis_MIDI LoopBack_device ( see the midlpbk.txt for install instructions ). Or if you use Windows XP, MIDI Yoke ( http://midiox.com/ ) looks good.
After Installing the loopback, configure SynthEdit for external MIDI Input, the file 'live.se1' is already set up to do this.
Set SynthEdit's MIDI input. menu 'Audio->Preferences, MIDI In' set this to LB1.
Set your sequencer track's MIDI output to the same loopback, LB1.
Push SE's 'Play' button, then switch to you sequencer. Any MIDI data sent should now go to SynthEdit.
If your sequencer supports audio tracks, you may need to select it's DirectSound driver for audio output.
Running a software synth alongside a sequencer is very demanding on the PC. For good timing you will need to minimise SynthEdit's latency ( Audio->Preferences->Play Ahead ). Unfortunately this will increase the processor load more. Setting SynthEdit's sample rate the same as the sequencer should help performance, but again, running SynthEdit at 44khz or more requires a lot of processor power.
One advantage of SynthEdit's internal MIDI Player is that you can use 'Offline Rendering'. By using the Wave Recorder module, SynthEdit writes the music to a wave file before playing it. In this mode you effectively have no CPU limitations. You can have as many Synth, Drum Machine or effects modules as you like. You can use 44, 48 or even 96khz sample rates with no problems.
You will find that using many Synths and effects at once will overload your CPU. Switching to 'File' rendering will overcome this, but you can't hear the audio while you make adjustments. To get around this, try Muting some of the modules (Right Click, 'Mute'). For example, once you have your drums mixed OK, mute them while you work on the bassline and lead sounds.