First of all, make sure you're using SCUMM Revisited 2. SCUMM Revisited 3 will not play back MIDIs.
The MIDIs and images of Sam and Max are stored in the file called something like samnmax.sm1. Open that file in SCUMM Revisited, and you'll see an entry (block) in the browser tree called LECF. Expand that, and you'll get more blocks - one LOFF block and a lot of LFLF blocks.
Expand one of the LFLF blocks, and you get more blocks (depending on which room is contained in this part of the file) - a ROOM block, some SCRP blocks (scripts), some COST blocks (character animations) and some SOUN blocks (sound effects and music - the voices are stored in the file called MONSTER.SOU). Some of those blocks may not be there. In that case, the room doesn't contain any sounds, or costumes, or scripts, depending on which type of block is missing.
If you find a SOUN block, expand that, and inside you'll find another block - SOU. Expand that, and you'll get the block you want - depending on the game and version, it's named something like SPK (internal speaker music), ADL (adlib music), GMD or GMID (General MIDI) or ROL (Roland MT-32 MIDI). Click on that one, and you should see the "Play" and "Save as .MID" buttons on the right (in the Block Specific Info box). Click one of those, depending on what you want.
Note that under WinXP, I've noticed SCUMM Revisited 2 making errors when playing MIDI. If you're using XP, you'll want to Save as .MID and open the file in your favorite MIDI player instead :)
Also, more generally, notice that these files are played exactly as they are. Meaning that since ADL files don't contain any instrument info, those blocks will sound weird. Since ROL files use different instrument numbers than the General MIDI standard your soundcard (and Windows) allows you to play by default, those will sound weird too. The only ones that will sound "right" are the GMD/GMID ones.
This also means that since iMUSE may use several different cues of music (which it jumps back and forth between as events occur in the game), and since all those cues are stored as different tracks which are placed "on top of each other" (iMUSE uses Standard MIDI File format 2 rather than the common format 1), a lot of times they may sound as total chaos when played back with SCUMMRev. You may want to open them in a MIDI sequencer and listen to each individual track - rather than all tracks at once.
Or, to avoid all the hassle, why not just download the files from
http://highland.mixnmojo.com) ? ;) Getting those MIDIs to sound as they sound in the game was what Andrew and I created HighLand for in the first place :) Although we only did the MIDIs that others hadn't done already (I think about 7 Sam and Max MIDIs had already been done - the ones that didn't have multiple cues) - those are available from other sites on Mojo. Don't remember which, though. Go look :)
As for the background images, do the same as above, but browse to the LECF/LFLF/ROOM/RMIM block. Then a View Image button should appear on the right.
Hope this helps :)
- Serge