It is principally lute societies which organise one-day playing events for lute players, and they publicise those organised by others; so visit the website of your national lute society, or contact them directly with enquiries.ice
If you are planning a lute playing day is a good idea to contact your national lute societies as they will certainly be able to put you touch with an experienced organiser for ideas and repertoire. It is generally best to find or choose an organiser, and if appropriate ask attendees each to bring a payment to the organiser, and perhaps food and drink for communal conviviality!
The most important thing is probably to have prepared repertoire for a variety of standards of player – also to ascertain what different sizes / keys of lute will be available.
The Lute Society has a library of scores for loan, which can be scanned or sent by post; see www.lutesociety.org/pages/travelling-library-of-lute-scores
There is also a small but growing range of arrangements for mixed ensembles, lute plus treble instrument etc, on the Free Downloads page: www.lutesociety.org/pages/free-downloads
Lots of lute ensemble arrangements can be found on the website of Sarge Gerbode: www.gerbode.net/composers/Lute_ensemble/ and Anton Hoeger has also produce numerous arrangements imslp.org/wiki/Category:Höger,_Anton
Some suitable repertoire is available commercially:
Secret de Muses, Volume 38 : Musique du XVe siècle pour luth solo et ensemble sf-luth.org/index.php?Partitions/Le_Secret_des_Muses
Les Petits Muses, Volume C : Musique du 16e siècle pour trio de luths. sf-luth.org/index.php?Partitions/Les_Petites_Muses
Another option is to take ground based duet and improvise more parts, starting with duets such as those found in the following
O Happy Ground, ed. Gordon Gregory, The Lute Society www.lutesociety.org/pages/catalogue#b
50 English Duets, Lundgren Edition luteonline.se/lundgren-edition/50_english.htm
Easy Pieces for Two Lutes, ed. Anne Bailes, from Tree Edition tree-edition.com/
Where more advanced players will be present:
The Thysius Lute Book quartets, published by Lundgren Edition luteonline.se/lundgren-edition/thysius.htm music in the style of Pacoloni, for slightly more instruments. Musically some are perhaps better than others.
Twenty One Pieces by John Dowland, Stewart McCoy´s arrangements of Dowland pieces for three lutes, with two more easy lutes ad libitum, also published by Lundgren Edition luteonline.se/lundgren-edition/dowland_trios.htm - these require a couple of pretty competent players for the top line, but ad lib parts 4 and 5 make simple duet versions.
Tobias Hume, Trios, originally intended as multi-use music, the top two parts are in tablature, the third plays from a bass line www.lutesociety.org/pages/catalogue#g
Lute Quartets edited by Ian Gaskell, a handy edition rounding up most of the extant lute quartets www.lutesociety.org/pages/catalogue#g
The trios of Pacoloni offer lots of good music, formerly published in facsimile by Minkoff of Geneva, now online at the Petrucci website, imslp.org/wiki/Tribus_testudinibus_lucenda_carmina_(Pacoloni,_Giovanni) though it may be advisable to consult Facebook groups or lute societies for modern scores.
Ten airs de cour for voice, flute, bass viol and five lutes, arr. Stefan Lundgren, www.luteonline.se/lundgren-edition/home_editions.htm Not currently listed on the webpage; enquire of the publisher.
One-day events for early music singers or instrumentalists, where lutes are welcome in multi-instrumental bands or to play continuo or accompaniments are held in many countries. National lute societies should be able to advise on these, but often they will be organised by more general early music organisations.
Early Music Review (UK based, includes a booklet of course, concert, festival and one-day event listings) subscribe at sites.google.com/site/earlymusicco/services related website earlymusicreview.com/
List of early music societies, can be found via:
National Early Music Association (UK based, by subscription): www.earlymusic.info/Register.php
Early Music Network (US based, by subscription):
In the UK the principal bodies organising one-day early music events are the regional early music fora, whom you should contact for events listings:
The Midlands: memf.org.uk
The North East: www.neemf.org.uk
The North West: nwemf.org/nwemf-workshops
Border Marches: www.bmemf.org.uk
Thames Valley: www.tvemf.org
South West: swemf.org.uk
Regional map: www.earlymusic.info/fora.php