I actually never installed in ~/Documents since I have bunch of audio repos etc in a directory called ~/Documents/workspace/AUDIO, but was wondering if installing into ~/Documents was a hardcoded requirement, but i just reread your comments and it looks like you got it working outside of that folder.
So now I have Linn and Rack in a folder called neauoire/ and linn works fine, but even with sudo npm install, Rack gives me the following:
WARN tar EISDIR: illegal operation on a directory, open '/Users/zeroship/Documents/workspace/AUDIO/neauoire/rack/node_modules/.staging/easymidi-36aa7c17/examples'
WARN tar EISDIR: illegal operation on a directory, open '/Users/zeroship/Documents/workspace/AUDIO/neauoire/rack/node_modules/.staging/easymidi-36aa7c17/tests'
WARN tar EISDIR: illegal operation on a directory, open '/Users/zeroship/Documents/workspace/AUDIO/neauoire/rack/node_modules/.staging/nan-e86cae03/doc'
WARN tar EISDIR: illegal operation on a directory, open '/Users/zeroship/Documents/workspace/AUDIO/neauoire/rack/node_modules/.staging/nan-e86cae03/tools'
WARN tar EISDIR: illegal operation on a directory, open '/Users/zeroship/Documents/workspace/AUDIO/neauoire/rack/node_modules/.staging/midi-f63ae4bd/test'
WARN tar EISDIR: illegal operation on a directory, open '/Users/zeroship/Documents/workspace/AUDIO/neauoire/rack/node_modules/.staging/midi-f63ae4bd/test/fixture'
WARN tar EISDIR: illegal operation on a directory, open '/Users/zeroship/Documents/workspace/AUDIO/neauoire/rack/node_modules/.staging/midi-f63ae4bd/src/lib/RtMidi/msw'
WARN tar EISDIR: illegal operation on a directory, open '/Users/zeroship/Documents/workspace/AUDIO/neauoire/rack/node_modules/.staging/midi-f63ae4bd/src/lib/RtMidi/autom4te.cache'
WARN tar EISDIR: illegal operation on a directory, open '/Users/zeroship/Documents/workspace/AUDIO/neauoire/rack/node_modules/.staging/midi-f63ae4bd/src/lib/RtMidi/doc'
WARN tar EISDIR: illegal operation on a directory, open '/Users/zeroship/Documents/workspace/AUDIO/neauoire/rack/node_modules/.staging/midi-f63ae4bd/src/lib/RtMidi/doc/doxygen'
WARN tar EISDIR: illegal operation on a directory, open '/Users/zeroship/Documents/workspace/AUDIO/neauoire/rack/node_modules/.staging/midi-f63ae4bd/src/lib/RtMidi/doc/images'
WARN tar EISDIR: illegal operation on a directory, open '/Users/zeroship/Documents/workspace/AUDIO/neauoire/rack/node_modules/.staging/midi-f63ae4bd/src/lib/RtMidi/tests'
WARN tar EISDIR: illegal operation on a directory, open '/Users/zeroship/Documents/workspace/AUDIO/neauoire/rack/node_modules/.staging/midi-f63ae4bd/src/lib/RtMidi/tests/Debug'
WARN tar EISDIR: illegal operation on a directory, open '/Users/zeroship/Documents/workspace/AUDIO/neauoire/rack/node_modules/.staging/midi-f63ae4bd/src/lib/RtMidi/tests/Release'
> midi@0.9.5 install /Users/zeroship/Documents/workspace/AUDIO/neauoire/rack/node_modules/midi
> node-gyp rebuild
gyp ERR! configure error
gyp ERR! stack Error: EACCES: permission denied, mkdir '/Users/zeroship/Documents/workspace/AUDIO/neauoire/rack/node_modules/midi/build'
gyp ERR! stack at Error (native)
gyp ERR! System Darwin 16.7.0
gyp ERR! command "/usr/local/bin/node" "/usr/local/lib/node_modules/npm/node_modules/node-gyp/bin/node-gyp.js" "rebuild"
gyp ERR! cwd /Users/zeroship/Documents/workspace/AUDIO/neauoire/rack/node_modules/midi
gyp ERR! node -v v6.13.1
gyp ERR! node-gyp -v v3.8.0
gyp ERR! not ok
npm ERR! code ELIFECYCLE
npm ERR! errno 1
npm ERR! midi@0.9.5 install: `node-gyp rebuild`
npm ERR! Exit status 1
npm ERR!
npm ERR! Failed at the midi@0.9.5 install script.
npm ERR! This is probably not a problem with npm. There is likely additional logging output above.
npm ERR! A complete log of this run can be found in:
npm ERR! /Users/zeroship/.npm/_logs/2019-07-12T17_56_39_122Z-debug.log
rack git/master 9s
❯```
UPDATE: killing the package-lock.json cut my errors in half to only permissions issues, but still strange. Maybe a versioning issue?