From what I gathered of the stats on the instruments <type>:<modifier>
Mistmoore Battle Drums:
Percussion Instruments: 21
21 = 2.1 or 210%
at level 5 running Selo's will boost your run speed 20%, if you have a mistmoore battle drum equipped it will amplify your song by 210% effectively giving you 42% run speed.
The same should hold true for the Lute of Gypsy Princess and the using a song like Hymm of Restoration.
Lute of the Gypsy Princess:
Stringed Instruments: 21
at level 6 the hymm gives 2 per tick, if the LotGP is equipped it should provide 4 (4.2) hitpoints per tick I assume this will be rounded down.
You can easily test this with the damaging songs.
http://wiki.project1999.com/Mistmoore_Battle_Drums
http://wiki.project1999.com/Selo%27s_Accelerando
http://wiki.project1999.com/Hymn_of_Restoration
http://wiki.project1999.com/Lute_of_the_Gypsy_Princess