I just recently started using SONAR LE.
I am recording into a laptop that has a single port that shares line in and line out (microphone/headphones).
SONAR records okay but the playback is, for lack of words, "suppressed".
The playback sounds good when the music dynamics are strong but it tends to "suppress" when the music is soft.
It is very obvious during those moments that the music does not sustain but abruptly cuts out.
I have always used MUSIC CREATER, so I'm not very familiar with SONAR.
What adjustments can fix this problem?

Hi . . . welcome to the forum !
So, it sounds like you are using the laptop onboard soundcard for recording ?
If you don't have a separate audio interface, you might get unexpected problems like this recording to a DAW such as Sonar. Most modern computers come with sound cards already built into the motherboard and are referred to as Integrated Sound Cards or Onboard Sound. Dedicated sound cards, the opposite of integrated, can be installed onto the system and are more convenient for professional audio recording.
 
Also, do you know what type of audio drivers are set up in Sonar preferences ? eg. Asio, WDM, MME, Wasapi

Welcome on my behaf as well :o)
I don't think there are any adjustments for such symptoms that don't exist in Music Creator as well. The basic record/playback-routing and handling is exactly the same, so they should sound exactly the same.
I'm slightly confused by your description of the issue.
How can you tell the recording is OK if you only have an output that sounds "suppressed".
How do you know the recording isn't "suppressed" as well if you haven't listened to it through another
(external) audio interface? Are you recording with a microphone or a line from a keyboard, or using also VSTi's?
 
Do you mean everything sounds ok when you monitor through headphones during tracking with "Input echo" enabled (that's when you hear the track output)? Or...oops...if you have only one combined in/out port, you can't monitor and use the mic simultaneously??? Have I understood correctly?
 
I guess you're auditioning with headphones - are they of decent quality? And the mic? Does this issue occur no matter what material is being auditioned - vocals, guitar, soft synths? If you're auditioning through laptop speakers, then it's fruitless to comment anything, because they are so bad anyway.

Noynekker / Kalle Rantaaho:
Thank you for your responses.
Noynekker, I am only using the built in sound card that came with my laptop.
I looked at the Audio options tab on my SONAR program and see that it has the options for WDM, WASAPI, ASIO & MME.
It is currently set at MME (32bit). Would changing it to one of the other's make a difference?
 
Kalle Rantaaho, I am basically playing a song on one laptop computer and recording it to a second laptop; using only
a 1/8in line jack to directly connect both computers. I haven't tried recording instruments or using a mic.
I did try playing back the recording on another external device (small sound system) and it was still the same.
 
The best way to describe what I mean by suppressed sound is that the playback sounds like a "wave" that goes from fairly
clear sound down to a low muffled sound, then back up to a clear sound, continuing that way throughout the entire playback.
Any suggestions? 

Is there a reason you're doing it in such a difficult way?
Wouldn't it be better and faster simply to copy the file on a memory stick and from that to the other computer?
The quality of the audio will degrade when the signal goes through two unnecessary AD/DA conversions.
My guess is the issue has nothing to do with SONAR, but is caused by some technical reason due to the "un-conventional" recording method. 
Are the laptops running on batteries or are they connected to the same wall plug? Could it be some type of ground loop or something similar?

It sounds like you are saying the music is loud when it is loud but too soft when it is soft. At least that is the way I would take:
"The playback sounds good when the music dynamics are strong but it tends to "suppress" when the music is soft."
 
If that is the case, then the problem is just low signal at those points. If the signal drops below what it takes to drive your speaker/headphone into the audible range you will get cutoff. Your meters should confirm that, and upping the gain on playback should make it less "suppressed," although it will likely make the normal part too loud. Ideally you should look into why the difference between the normal and soft/suppressed (dynamic range) is so large when you are recording in the first place. A compressor plugin can reduce the loud parts so that they will not clip or break your ears or speakers while you increase the gain to raise the soft parts relative output volume.
 
Note that there is a big difference between how loud music sounds on playback (the volume) and how it is recorded, which for want of a better word is saturation. Volume of even very "soft" recording can be amplified on playback, although with some potential for distortion. Music that is recorded with peaks near the zero dB on your SONAR meters is fully saturated, it has digital data that is nearly as many bits as you can accurately represent. Parts of the recording that drop too many bits/dB below the peaks will present a problem like you describe. If you try to raise the saturation level on the recording to bring the relative soft parts up, you are likely to raise the peaks above what digital data can represent (clipping or digital over). That will definitely cause some very nasty distortion. That is the problem a compressor is designed to handle by effectively subtracting more bits from the louder parts relative to the softer parts.