Dear Prof Tieken,

Here are some references to the mārjana /anulēpana of the Mr̥daṅga and other kindred drums.

1. A gāhā from the Sattasaī speaks of the coating of rice that makes the timbre of the drum sweet. It appears that the Sanskrit verse  को न याति  etc. is a later (pale) paraphrase of this one.

aülīṇo domuhao tā mahuro bhoaṇaṃ muhe jāva / HSS_253ab
murao vva khalo jiṇṇammi bhoaṇe virasam ārasaï / HSS_253cd
 
2. In Cilappatikāram book 28, in the description of the Cākyār's dance, is a drum that is smeared with mud (maṇ kaṇai muḻavum). You have probably seen the passages in Bharata and Śārṅgadēva describing the smearing of mud.

3. A line from Bāṇabhaṭṭa's Kādambarī that speaks of how the coating makes the sound of the drum sonorous - especially when it is freshly applied -

kad pb1.133 atha nāticirād evānulepanārdra-mṛdaṅga-dhvani-dhīreṇa nirvivara-vijṛmbhita-pratināda-gambhīreṇa, śabaraśaratāḍitānāṃ keśariṇāṃ ninādena, [....] vanāntaravyāpinā dhvānena sarvataḥ pracalitam iva tad araṇyam abhavat /

4.  In the contemporary Indian drums  pakhāvaj and  mṛdaṅga, one can see two kinds of coating - one is a (more or less permanent) black circle of clay, starch and iron filings that is fixed in the centre of the membrane - this is usually done by a professional technician.  It is pertinent that this tuning paste is also called cōṟu (cōṟṟu). The other is a (temporary) circle of  cooked rice or semolina paste applied on top of the black spot by the drummer before they perform on the mṛdaṅgam. In the case of the Pakhāvaj drum, a dough of wheat flour is applied.